Blueprint of Life 1

BLUEPRINT OF LIFE

BLUEPRINT OF LIFE

(Last updated 5th May 2011 by SR/IR)

CONTEXTUAL OUTLINE:

Because all living things have a finite life span, the survival of each species depends on the ability of individual organisms to reproduce. The continuity of life is assured when the chemical information that defines it is passed on from one generation to the next on the chromosomes.

Modern molecular biology is providing opportunities to alter the information transferred from one generation to the next in technologies such as cloning and in the production of transgenic species.

The segregation and independent assortment of the genetic information within a species provides the variation necessary to produce some individuals with characteristics that better suit them to surviving and reproducing in their environment. Changes in the environment may act on these variations. The identification of mutations and their causes becomes important in preventing mutations and in identifying and potentially nullifying the effects of mutations in living organisms.

Outline the impact on the evolution of plants and animals of:

changes in physical conditions in the environment

changes in chemical conditions in the environment

competition for resources

Things to consider:

What does outline mean?

What is the question asking?

Underline key words

There have been many factors that have impacted on the evolution of plants and animals. The following are some impacts that have altered the evolution of plants and animals:

Changes in chemical conditions in the environment:

Life has been evolving for millions of years. Early earth was an anoxic environment which meant there was no free oxygen. The organisms during the anoxic period metabolised simple organic molecules. A product of this was carbon dioxide. Eventually the build up of carbon dioxide led to the evolution of photosynthetic organisms (plants) that metabolised the carbon dioxide to produce energy and oxygen. This in turn led to the environment changing from anoxic to oxic. This in turn also meant that plants started to evolve according to the environment as well as animals. As more and more plants evolved many more animals evolved due to the food chain.Other reasons as to how plants/animals evolve:

DDT

Antibiotics

Changes in physical conditions in the environment:

The Earths conditions are constantly changing. Due to these changes organisms are constantly evolving. The following are some reasons as to why organisms have evolved:

Sea levels

Land formations (fossil evidence)

Meteorite which formed a dust cloud changed the environment (theory)

Continental drift

Volcanoes (similar effect as the meteorite)

The above reasons illustrate that organisms must have evolved according to the conditions they faced at the time. Fossil evidence has shown many changes which indicate a change in the environment. One key Australian example is the evolution of the eucalypt. Australia was once covered by lush beech forest. As Australias climate changed so to did its vegetation. The soils became drier and the rainfall dropped. This in turn led to the evolution of the eucalypt.Therefore, it is evident that changes in the physical environment have led to the evolution of plants and animals.

Competition for resources:

Competition for resources usually results in the extinction of a species or a species occupying another niche. There have been many cases whereby competition for resources has led to the evolution of another species. One Australian example is the flycatcher. Due to this species having the same diet there has been diversification of the species. A whole new species has evolved to occupy a different niche. The leaden flycatcher catches its prey around trees while the restless flycatcher catches its prey just above the ground by emitting a call that disturbs the insects. This example shows that if the flycatcher had not evolved, occupying a separate niche, there would have been competition for resources and in turn the species may have become extinct.Describe, using specific examples, how the theory of evolution is supported by the following areas of study:

palaeontology, including fossils that have been considered as transitional forms

biogeography

comparative embryology

comparative anatomy

biochemistry

Things to consider:

What does describe mean?

Underline key words

How would you go about answering this question

Outlined below are specific examples which support the theory of evolution:

Palaeontology, including fossils that have been considered as transitional forms:

Palaeontology, the study of fossils is a specific example that accounts for the theory of evolution. Fossils are formed under strict circumstances and include such traces as bones, teeth, footprints and faeces. There are many reasons as to why fossils aid in the theory of evolution. Firstly fossils can be compared structurally. This can lead to evolutionary relationships and explain an evolutionary pathway. Secondly through carbon dating fossils can be dated as to when they formed/existed. Knowing how old a fossil can determine evolutionary relationships. Thirdly knowing the type of rock the fossil formed in can indicate the time the fossil was formed. Comparing this fossil to another fossil found in the same rock helps scientists make comparisons between the two fossils. Fourthly transitional fossils support the theory of evolution. Archaeopteryx is a transitional fossil that illustrates the relationship between dinosaurs, reptiles and birds. The lobe fin fish is a transitional fossil that illustrates the evolutionary pathway of fish to amphibians.

Therefore from the above evidence palaeontology supports the theory of evolution as it illustrates evolutionary relationships between organisms.Biogeography:

Biogeography supports the theory of evolution in many ways. Firstly Darwin and Wallace, through their studies identified that there were striking similarities between current organisms from differing countries. (As well as fossils.) This eventually led to the fact that continental drift affected evolution. This is supported by: Pincushion coneflower (South Africa) VS Holly Leaved Banksia (Australia)

Opossum in South America and its closest relative in Australia.

The above evidence suggests that these landforms were previously much closer together. Over time these continents drifted apart causing the organisms of that continent to evolve according to its environment.Comparative embryology:

Comparative embryology supports the theory of evolution. The embryos of the fish, salamander, tortoise, chicken, pig, rabbit and human are all very similar in embryonic stage. These organisms then evolve with each structure having a different specialised function, supporting the theory of evolution.Comparative anatomy:

Comparative anatomy supports the theory of evolution in a number of ways. It is evident that the fore limb also known as the pentadactyl limb supports the theory of evolution. The limb has a similar structure in many organisms; however the organism has evolved to use that limb for a specialised function such as swimming or flying.Biochemistry:Biochemistry supports the theory of evolution including evolutionary relationships and evolutionary pathways. Virtually all organisms use cytochrome C, a protein, for energy. Through studies of this protein scientists can compare the similarity between organisms. A change in DNA leads to a different amino acid sequence which in turn produces a different organism. The study of biochemistry therefore supports the theory of evolution. Explain how Darwin/Wallaces theory of evolution by natural selection and isolation accounts for divergent evolution and convergent evolution.

Things to consider:

What does explain mean?

What is natural selection?

What is isolation?

What does account mean?

Background info:

NATURAL SELECTION: is the process by which an organism will adapt to its environment due to natural pressures such as the environment or competition. This leads to desirable characteristics being passed on from one generation to the next. Also known as survival of the fittest. e.g. Peppered moths in England.ISOLATION: is the process by which a group of organisms is isolated from the original species. This new group usually undergoes natural pressures such as environmental change. This leads to mutation and natural selection which in turn produces a new species. e.g. The apple maggot fly and the Hawthorn maggot fly.

ADAPTIVE RADIATION: the process by which an organism adapts to its niche over millions of years.

Darwin and Wallaces theory of natural selection and isolation accounts for divergent evolution. For example when a species is occupying a certain environment it will be exposed to those environmental pressures. This organism will adapt and continue to evolve over thousands and millions of years, according to these environmental pressures, (natural selection.) However, this same species may become separated or isolated due to flood waters, mountain ranges or even deserts, (isolation.) This then means this organism, due to its new environmental pressures evolves according to its new niche, (natural selection.) Evolution of this species continues to occur until the species become two separate species and are no longer able to reproduce with one another. This is known as divergent evolution. (A species diverges from its original species.)

Darwin and Wallaces theory of natural selection and isolation accounts for convergent evolution. Convergent evolution is the process by which organisms with different ancestors have acquired the same characteristics according to the similarity of their niche. Analyse information from secondary sources to prepare a case study to show how an environmental change can lead to changes in a species.Things to consider:

What does analyse mean?

Underline key words

Ensure you use an example to show how environmental change can lead to changes in the species. e.g. Red kangaroo

A chief example of an environmental change that lead to a change in a species were the peppered moths in England. Peppered moths are either pale in colour or dark in colour. In an unpolluted area the pale moths are well camouflaged by the lichen on the surrounding trees, while the darker moths are much easier to see. The birds within the ecosystem prey on the darker moths as they are much easier to see. This then equates to the paler moths occupying the ecosystem and passing on the desirable characteristic of the pale colour.

However, due to an environmental change the darker moths have flourished. Due to industrial pollution the trees within the area have darkened in colour. Consequently the darker moths have greater camouflage compared to that of the paler moth. This in turn means that paler moths are picked off by the bird population; therefore the darker moths through years of natural selection have a higher survival rate in a polluted area.

TREE COVERED IN LICHEN. (CAN YOU SEE THE PALER MOTH)

TREE AFFECTED BY POLLUTION. NOTE THE DIFFERENCES BETWEEN THE TWO PICTURES.Perform a first-hand investigation or gather information from secondary sources (including photographs/ diagrams/models) to observe, analyse and compare the structure of a range of vertebrate forelimbs.Things to consider:

What does observe, analyse and compare mean?

Ensure you include diagrams in your research.

ORGANISMSTRUCTURE/FUNCTIONPICTURE

Crocodile The crocodile has a short structured forelimb which contains five digits, a humorous, ulna and radius. The forelimb is quite compact with the ulna and radius packed tight together while the humorous is short and quite dense. The angle of the forelimb suggests that the crocodile uses this limb for pushing off, wading in water and walking on land.

HumanThe human forelimb is long in structure. It contains five digits, a humorous, ulna and radius. The humorous is the largest bone. It is thin and long in nature. The ulna and radius are similar in size and structure; they connect to the carpals and phalanges. The human forelimb has many functions including balance.

BirdThe birds forelimb contains a humorous, ulna, radius and three digits. The bones are at different angles suggesting that at rest the forelimb folds up. The density of the humorous, ulna and radius are quite similar. The function of the birds forelimb is mainly for flying.

BatThe bats forelimb is thin in structure and contains a small humorous, thin ulna, thin radius and five long digits. The angle of the bones suggests that the limb folds up when not in use. The bones are quite thin suggesting that the creature is small and light. The main function of this limb is for flying.

WhaleThe Whales forelimb is very dense in structure. It contains a large square humorous, an ulna, a radius and five digits. Due to the structure of the whales forelimb it appears that the whole limb moves as one. Therefore, it is apparent that the main use of the whales forelimb is for swimming.

FrogThe frogs forelimb contains a humorous, ulna and radius. The humorous is long and thin in structure while the ulna and radius are short and thin in structure. The five digits are long and thin in structure. The function of the forelimb is for balance and to some degree pushing off the ground.

Use available evidence to analyse, using a named example, how advances in technology have changed scientific thinking about evolutionary relationships.

Things to consider:

What does analyse mean?

Ensure you use an example to explain your answer

Relate your example to evolutionary relationships

One example of an advance in technology that has changed scientific thinking about evolutionary relationships is DNA hybridization. DNA hybridization is used to identify the similarities between two different organisms by comparing their DNA. The process of DNA hybridization is outlined below. 2 strands of DNA are collected. One from one species the other from another species.

These 2 strands are heated which causes the strands to separate.

One strand from each organism is then combined to form a hybrid. Not all of the bases in each sequence will match up.

Pairing of the DNA strands depends on the similarities of the organisms being compared. Organisms are said to have come from a recent ancestor if their sequence is highly similar. Conversely if the sequence has a low degree of pairing the organisms are said to unalike.

DNA hybridization has changed scientific thinking about evolutionary relationships as it directly enables scientists to compare organisms genetically. This process allows scientists to determine whether a species recently diverged from a common ancestor or diverged from a common ancestor a very long time ago. Therefore it is evident that this advance in technology has changed thinking about evolutionary relationships.Analyse information from secondary sources on the historical development of theories of evolution and use available evidence to assess social and political influences on these developments.

Things to consider:

What does analyse and assess mean?

Underline key words

Be succinct

HISTORY:

The main constituents of evolutionary theory were Darwin and Wallace. Darwin, a naturalist is recognised mostly for his work in South America. Darwin sailed to the Galapagos Islands in the 1830s on his ship called the beagle to observe the local flora and fauna. What he discovered was the beginning of his theory on natural selection. In Darwins observations he noticed that depending on the island and the habitat certain finches, from a common ancestor, portrayed different physical characteristics. The main characteristic Darwin concentrated was the shape of the finchs beak. He noticed that the finches had acquired a certain shaped beak according to their niche. Darwin concluded that: All these finches came from a common ancestor.

The finches then occupied individual niches.

These niches had an abundance of food.

Over time the finchs evolved a beak according to the food they ate.

Darwin concluded by calling his theory, The Theory of Natural Selection.

At the time of Darwins research another scientist by the name of Wallace was completing similar research in Indonesia. In Indonesia it has been documented that Wallace collected 125 660 species, producing over one thousand new species to science. Through his research he was coming to similar conclusions to that of Darwin. He sent his research and documentation to Darwin, who in turn subsequently produced the book The Origin of Species. Darwin and Wallace have both been attributed with the theory of natural selection.

SOCIAL AND POLITICAL INFLUENCE:

Darwins book caused uproar among certain English social and political groups. People could not believe in the theory of evolution because at that time it seemed completely impossible and a threat to religious, social and political beliefs.

However, through further scientific research and support the theory of natural selection has become more accepted in social and political groups. This is evident in the 1860s where groups borrowed the ideas of Charles Darwin and transferred them to the social domain. They proposed that societies could evolve just like plants or animals. This view was known as social Darwinism and was proposed by Herbert Spencer. This theory rose to prominence in the late 19th and early 20th century. Spencer suggested that life was a struggle an only the people who were the fittest would survive (not documented). This directly had an impact on social and political influences.Social Darwinism is outlined below:

Struggling for existence within society was part of evolution.

This meant only the fittest members of society would survive.

Weakest members would fail.

State Reforms were said to interfere with evolution. (Welfare) Social classes were natural.

Also influenced political groups. The stronger/fitter groups would run the nation. Governing over the weaker.

War was a positive as it was seen to eliminate the weakest.

Subsequently through common sense biological evolution no longer is applied to social groups. E.G. poverty can not be attributed to laziness.

Therefore, it is evident that Darwins/Wallace theory of natural selection did have an impact on social and political groups. Plan, choose equipment or resources and perform a first-hand investigation to model natural selection.

Things to consider:

What does plan mean?

Underline key words?

Ensure your experiment models natural selection.

AIM:

To use coloured tooth picks to models natural selection.

MATERIALS:

20 green tooth picks

20 red tooth picks

METHOD:

1. Mark out an area of approximately 1metre x 1metre on a grassed area.

2. Group member 1 is to place the tooth picks within the marked out area while the group member 2 is looking away.

3. Group member 1 then instructs group member 2 to turn around and collect as many tooth picks as possible over 10 seconds. Group members are then to record their result in their results table.

4. Repeat steps 2 and 3 five times.

RESULTS:

TRIALNO. OF GREEN TOOTH PICKSNO. OF RED TOOTH PICKS

1

2

3

4

5

QUESTIONS:

1. Identify any control(s) you used in this experiment.

The controls we used in this experiment were;

The amount of tooth picks (20)

The area in which we dropped the tooth picks

The time allocated to picking up the tooth picks

2. Identify the independent variable(s) of this experiment.The independent variable of this experiment was the colour of the toothpicks.

3. Identify the dependent variable(s) of this experiment.The dependent variable of this experiment is the amount of tooth picks that are picked up.

4. How does this experiment model natural selection?

The purpose of this experiment was to model natural selection. The green tooth picks were to blend in with the natural surroundings that being the grass while the red tooth picks were meant to stand out. This example in an ecosystem would mean that the red tooth picks would be easier to see therefore easier to pick off, by a predator. This experiment also relates to the peppered moths in England.

Outline the experiments carried out by Gregor Mendel.

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Be succinct

Gregor Mendel was one of the first scientists to research and develop ideas about genetics and the passing on of genes from one generation to the next. He performed many experiments which supported his research. One of these experiments involved crossing two pea plants. Mendel crossed a homologous tall pea plant with a homologous short pea plant. These parents produced all tall offspring. He called this generation the F1 generation, F meaning filial (son). Mendel then interbred all of the first generation. The first generation then produced a range of tall and short plants in the ratio of 3:1. (Generation 2 F2) The experiment performed by Mendel was accurate, valid and reliable because he used pure breeding plants and he yielded large results. He produced over 400 plants as part of generation 2 and still managed to have a ratio of 3 to 1. (REFER to p. 137 to 141)

Other outcomes of Mendels experiments:

The law of segregation- Mendel established that all organisms carry factors (genes). These factors control characteristics. These factors at the point of reproduction separate. They then pair up with another factor. The dominant factor will be expressed.

The law of independent assortment- This law basically states that chromosomes separate independently of one another and are arranged in the gamete independently of one another. Describe the aspects of the experimental techniques used by Mendel that led to his success.

Things to consider:


Underline key words

Understand what the question is asking before you answer the question.

There are five main points that led to Mendels success. They are:

He studied a large number of characteristics. Concentrating on one characteristic would have been an arduous task. Broadening the field for certain characteristics enabled Mendel to produce a larger set of results.

He carried out a large number of crosses. Mendel completed a large number of crosses which in turn yielded more plants. This large result would have made his research and conclusions more accurate and reliable as he repeated the process and obtained similar if not precise results over and over.

He used pure breeding lines. This enabled Mendel to concentrate on certain characteristics. Pure breeds are homozygous which means they carry two identical genes either being recessive or dominant. Pure breeding plants also enabled Mendel to obtain reliable and accurate results.

He made exact counts of characteristics. Exact counts of characteristics produced quantitative data which enabled Mendel to analyse and make conclusions about his results.

Mendel studied separate identifiable characteristics. This enabled Mendel to concentrate on characteristics which could be seen and easily documented.

Ultimately the stringent criteria that Mendel followed led to the discovery of genetics.

Outline the reasons why the importance of Mendels work was not recognised until some time after it was published.

Things to consider:


Underline key words

Use scientific language

There are many reasons as to why Mendels work was not recognised until some time after it was published. Firstly he only presented his work to a small group of scientists. These scientists may not have understood his research as it was a new concept or they understood his work but did not realise the significance of it. Secondly Mendel was not a famous scientist. He was an Austrian monk who worked in a small team within his monastery. He worked quietly with his team and then produced and published his results from obscurity. This may have been one reason as why his work was not received with open arms.

Biological research began to evolve in the 1900s where Mendels work became recognised. Subsequently through his research Mendel became known as the father of genetics.

Describe outcomes of monohybrid crosses involving simple dominance using Mendels explanations.

Things to consider:


What is a monohybrid cross?

Ensure you include Mendels explanations in your answer.

Monohybrid crosses are crosses which involve only one specific characteristic. These characteristics could include eye colour, hair colour or in Mendels case the height of pea plants. When performing a monohybrid cross we need to obtain certain information. Information necessary to produce a cross includes whether or not the cross is between homozygous or heterozygous pairs and whether or not the characteristic is dominant or recessive. For example Mendel crossed a homozygous tall pea plant (TT) with a homozygous short pea plant (tt). We know that the tall gene is the dominant gene because the first generation of plants were all tall. Some of the first generation, although all tall, would have been carrying a short gene. This in turn was shown in the second generation whereby the short gene was expressed in the ratio of 3 tall plants to 1 short plant. Through simple monohybrid crosses scientists are able to determine the dominance of a gene as well as hypothesise what the outcome could be between certain crosses involving certain characteristics.Distinguish between homozygous and heterozygous genotypes in monohybrid crosses.

Things to consider:

What does distinguish mean?

Underline key words

Best way to represent this information?

HOMOZYGOUSHETEROZYGOUS

Homozygous genotypes are pure bred for that specific characteristic.

Homozygous alleles are either both dominant and recessive.

Dominant homozygous alleles are always expressed as capital letters. e.g. AA.

Recessive homozygous alleles are always expressed as lower case letters. E.G. aa.

The letters used to illustrate the specific characteristic are known as the genotypes. Heterozygous genotypes contain different alleles that express different characteristics.

Heterozygous alleles always contain a dominant gene and a recessive gene.

Heterozygous alleles are always expressed as a capital and then a lower case letter. e.g. Aa.

The letters used to illustrate the specific characteristic are known as the genotypes.

Distinguish between the terms allele and gene, using examples.

Things to consider:

What does distinguish mean?

Ensure you use examples in your answer

ALLELEGENE

Alleles are pairs of genes situated in the same location on a homologous pair of chromosomes.

Alleles contain information for the same characteristic but not necessarily the same information. For example, the allele will be for hair colour. One allele could specify for brown hair while the other allele could specify for blonde hair.

Genes are found on all chromosomes. Each gene can be represented as a band on a chromosome.

In a double stranded chromosome each gene is represented twice as indicated below.

Genes code for certain characteristics. For example certain genes according to their chemical make up code for hair colour or eye colour.

Explain the relationship between dominant and recessive alleles and phenotype using examples.

Things to consider:


Underline key words

Be succinct

When considering phenotypes we need to keep in mind whether or not certain alleles are dominant or recessive. Dominant alleles dominate over other alleles and are always expressed. When expressing dominance in a cross the letter is always written as a capital. Recessive alleles are rarely expressed in an offspring. The only occasion when recessive alleles are expressed is when there is an absence of a dominant gene. Dominant and recessive alleles can be linked to the phenotype of an offspring. The phenotype of the offspring is the actual physical characteristic that is being expressed. For example, a dominant black haired person (BB) produces offspring with a recessive blonde hair person (bb).

BB

bBbBb

bBbBb

As indicated by the punnet square above 100% of the offspring will have the phenotype of black hair. This is represented by all the alleles containing a capital B (dominant) and a lower case b (recessive). Perform an investigation to construct pedigrees or family trees, trace the inheritance of selected characteristics and discuss their current use.

Things to consider:

What does perform mean?

What does discuss mean?

Underline key words

Understand what the question is asking before you complete the question.

Refer to family tree produced in example below. Then answer questions. Suggested answers have been supplied.

QUESTIONS 1 4 ARE BASED ON A FAMILY TREE EXAMPLE.5. Family trees can be used to provide genetic counselling. The family tree in figure 12.1 shows the occurrence of a rare lung disease, which is caused by a recessive gene. Children suffering from the disease rarely live more than 2 years. The probability of an individual in the population carrying the recessive gene is about 1 in 400 (1/400).

(a) There are no known cases of the disease among any of Marinas relatives. Prior to Jen and Bob having children, what would have you estimated the probability of them having a child with the disease would be?

(b) After having Sue and Sean, what would the probability have been of the next child suffering the disease?

(c) After having Marina, what is the probability that their fourth child might have the lung disease?

(d) Use a punnet square to show the genotypes of Jen, Bob, Sue, Sean and Marina.

(e) If you were providing genetic counselling to Jen and Bob, what would you tell them?

(f) Su Chi and Mark have not yet had children. If you were providing genetic counselling to them, what would you tell them?

(g) Research genetic counselling to find out how the prospective parents are advised. Compare the type of information provided with the advice you gave.

ANSWERS:(a) Due to the nature and the prevalence of the disease I would have estimated that there would have been an extremely low to zero possibility that Jen and Bob would have a child that would suffer from the lethal lung disorder.

(b) Due to the nature of punnet squares and probability, and knowing the outcome already of the family tree it was a 50% chance that the next child could have the disease. However prior to having this child, the nature of the disease and knowing that no other member of the family had the disease it would also be accurate in saying that there was 0% chance of the next child having the lung disease.

(c) Due to the disease being a recessive disease the probability that the next child will have the disease is 0%.

BOBJEN

Ll

LLLLl

lLlll

L = Healthy lungsl = The recessive gene for the lung disorder

The following are the possible genotypes of the parents and their offspring.

Jen = Ll

Bob = Ll

Sue = LL or Ll

Sean = LL or Ll

Marina = ll

(d) If I was providing genetic counseling for Jen and Bob I would tell them that it is extremely rare for them to conceive another child with the disease. It is almost a zero percent chance that there next child would have the disease. I would also tell them that there other healthy children; Sue and Sean could possibly be carrying the recessive gene for the disease based on probability.

(e) If I was providing genetic counseling to Mark and Su Chi I would tell them that it would be extremely rare that they would have any offspring that would have the disease. Based on the family tree Mark is highly unlikely to be carrying the recessive gene.

(f) Genetic counseling is a process undertaken by professionals whereby a family pedigree is assembled and assessed according to the parents genetic variations. All variables such as certain diseases and hereditary problems are discussed with the parents. Parents are informed of the chances of whether their offspring will have a certain disease or not. The genetic counselor then offers advice on community programs or a plan of care for the child. This is often passed onto the family physician. This type of information is similar to the advice I gave. However, a plan of action was not discussed nor the probability of other diseases.

Solve problems involving monohybrid crosses using Punnett squares or other appropriate techniques.

Things to consider:

What does Solve mean?

What is a monohybrid cross?

Students are to complete questions 1 5 on page 151 of the textbook.1. (a) Bb (All black)(b) 1BB : 2 Bb : 1bb (3 black : 1 white)(c) 2Bb : 2 bb (2 black : 2 white)2. (a) Cc (C is curly wing c is straight wing)(b)Cc

CCcCc

cCccc

Genotypes = CcPhenotypes = 3 curly wing : 1 straight wing (c) Cc

CCCCc

cCccc

Genotype = CC : Cc : cc 1 : 2 : 1

25% : 50% : 25%

Phenotype = Curly : Straight 3 : 1 (75% : 25%)3. (a) The green pod must be dominant as it mask the yellow pod gene in the heterozygous peasGG

gGgGg

gGgGg

Genotype = Gg : Gg

100% GgPhenotype = All green pods(b) Gg

GGGGg

gGggg

Genotype = GG : Gg : gg 1 : 2 : 1

25% : 50% : 25%

Phenotype = Green : Yellow 3 : 1 (75% : 25%)4. (a) Jordan is bb. Claire is Bb. Chloe is bbWhy does Jordan have blue eyes? This answer depends on the phenotypes of the parents. Consider all possible phenotypes:

BB x BB

BB x Bb

Bb x Bb

BB

BBBBB

bBbBb

Bb

BBBBb

bBbbb

BB

BBBBB

BBBBB

Genotype = BB Genotype = BB : Bb Genotype = BB : Bb : bb

1 2 : 2 1 : 2 : 1

100% 50% : 50% 25% : 50% : 25%

Phenotype = Brown eyes Phenotype = Brown eyes Phenotype = Brown : Blue

1 4 3 : 1

100% 100% 75% : 25%

Therefore the only possible chance that two brown eyed parents have a blue eyed baby is if both there genotypes are Bb. This means that the parents have a 25% chance of having a blue eyed baby.Bb

bBbbb

bBbbb

(b)

Genotype =Bb : bb

2 : 2

Phenotype = 2 brown : 2 blue

The chance of having another blue eyed child is 50%

5. A test cross is when you cross your unknown with a homozygous recessive to test if there your unknown has a hidden recessive gene.The brown guinea big you are testing could be homozygous brown or heterozygous brown. This answer depends on the phenotypes of the parents. Consider all possible phenotypes:

BB x bb Bb x bbBb

bBbbb

bBbbb

BB

bBbBb

bBbBb

Genotype = Bb

Genotype = Bb : bb

1 2 : 2

100% 50% : 50%

Phenotype = Brown Phenotype = Brown : White

1 2 : 2

100% 50% : 50%

Process information from secondary sources to describe an example of hybridisation within a species and explain the purpose of this hybridisation.Things to consider:

What does process mean?



Firstly hybridisation is the pairing between single stranded complimentary DNA segments from organisms from the same or even different species.

If we look at hybrid plants, hybrid plants are a more vigorous and higher yielding plant compared to that of their homozygous parents. A specific example of hybridisation in plants is hybrid corn. The reason why farmers produce hybrid corn is the fact that the plant is a much stronger plant as well as producing a greater yield of corn which in turn produces more money for the farmer.In the 1930s corn production was increased due to farmers interbreeding corn which produced large fruit while the other breed of corn was a sturdy vigorous plant. The result from this cross was a hybrid that was strong, vigorous and produced large fruit.

Ultimately the purpose of hybrids is to increase the genetic pool of a certain organism. This increases the likelihood that a desirable plant/animal will be produced. On the other hand hybridisation can produce unwanted characteristics. For example, if a horse reproduces with a donkey the resultant offspring is a mule. Mules are infertile this means that they can not reproduce, which in turn eliminates the species. Therefore, hybrids are chosen in certain circumstances to produce high quality reproducing plants and animals.

Outline the roles of Sutton and Boveri in identifying the importance of chromosomes.

Things to consider:


Ensure you learn these scientists contribution to biology as scientists are frequently referred to in the HSC.

Be succinct.

In 1902 Sutton proposed a chromosomal theory of inheritance. Sutton built his theory around Mendels work, where Mendel concluded that inheritance was due to certain factors (genes). Sutton elaborated on Mendels work to suggest that genes were carried on chromosomes. Sutton discovered this while observing meiosis in grasshoppers. His findings were as follows:

During meiosis in grasshoppers the chromosomes lined up in pairs.

Each pair of homologous chromosomes separate so that each gamete receives the same amount of chromosomes.

After fertilisation the zygote had a full set of chromosomes. (Half from male half from female.)

At around the same time as Sutton, Boveri drew a link between hereditary characteristics and chromosomes. Together these two scientists were recognised as the founders of the chromosomal theory of inheritance. Their research into the activities of chromosomes showed that chromosomes are the mode for inheritance.

Describe the chemical nature of chromosomes and genes.

Things to consider:


Identify the chemicals first then their chemical make up.

Genes are organised into larger structures known as chromosomes. These chromosomes carry many different genes containing different types of information such as hair colour and eye colour to name a few. Each chromosome (genes are within a chromosome) is made up of approximately 60% protein and 40% DNA. This means that chromosomes contain many different amino acid sequences which make up proteins. As chromosomes are made up of DNA chromosomes and genes would contain the chemicals adenine, cytosine, thymine guanine, various types of sugars and phosphates. These bases are responsible also for the chromosome containing a large amount of protein.

Identify that DNA is a double stranded molecule twisted into a helix with each strand comprised of a sugar phosphate backbone and attached bases adenine (A), thymine (T), cytosine (C) and guanine (G) connected to a complimentary strand by pairing the bases, A T and G C.

Things to consider:

What does identify mean?

The dot point basically states the answer within it. Ensure you understand the structure of DNA.

The DNA molecule is referred to as a double stranded helical structure. If you were to unwind this structure so that it lay flat it would look like a ladder. The DNA molecule is made up of a number of subunits called nucleotides. Nucleotides are comprised of a sugar generally represented by a pentagon in a diagram, a phosphate generally represented by a black dot and one base varying from adenine (A), thymine (T), cytosine (C), and guanine (G). These bases can only match up to the corresponding base. For example, in the DNA double helix structure A can only match up to T and G can only match up to C.

For example if my DNA strand was:

AATCGCTTAGCT

The complimentary strand would be:

TTAGCGAATCGA

DNA MOLECULE

http://www.biologycorner.com/resources/DNA-colored.gifNUCLEOTIDE:

NOTE: The nucleotide is highlighted by the box above.

http://www.accessexcellence.org/RC/VL/GG/images/nucleotide.gifExplain the relationship between the structure and behaviour of chromosomes during meiosis and the inheritance of genes.

Things to consider:


Understand what you are going to write before you write an answer.

Be succinct

Chromosomes behave in certain ways during meiosis so that the inheritance of genes is a possibility. Firstly in meiosis the chromosomes line up in homologous pairs on the equator of the cell. Each of these chromosomes contain many genes. Genes are the building blocks of inheritance; they contain information for specific characteristics such as hair colour. As the chromosomes split up and sorted they move to different daughter cells. These daughter cells divide again to produce four new cells. During the production of these daughter cells crossing over occurs. Crossing over is the process whereby chromosomes swap genetic information which in turn causes variation from daughter cell to daughter cell. Crossing over does not occur every time the chromosomes line up on the equator of the cell. The closer the chromosomes are in characteristic the less likely crossing over is going to occur the further apart they are in characteristics the more likely crossing over will occur.

Therefore, during meiosis chromosomes act in a certain behaviour this causes a variation of inheritance in all daughter cells.

Explain the role of gamete formation and sexual reproduction in variability of offspring.

Things to consider:


Underline key words.

Understand the key words before you answer. For example what does variability mean?

Gametes also known as sex cells (sperm and ova) are produced in the testicles of the male and the ovaries of the female. Gametes are haploid (n = 23) which means they contain half the number of chromosomes compared to a normal cell which contains a diploid (2n = 46) number of chromosomes. During meiosis crossing over occurs. Crossing over causes all the gametes to vary in their characteristics meaning none of them are the same. All gametes are unique and are different from their parent.As stated above all gametes vary genetically due to meiosis. In sexual reproduction two gametes (sperm and egg) are brought together. These gametes fuse together to form a diploid (46 chromosomes) zygote. This new organism is a unique combination of genes inherited from the parents. Sexual reproduction causes variation within a species for the following reasons:

Fertilisation is based on chance. Gametes are not pre chosen to fuse together.

Meiosis causes a huge pool of unique gametes. The chances that a genetically identical sperm and egg fuse together is nearly impossible.

Describe the inheritance of sex linked genes, and alleles that exhibit co dominance and explain why these do not produce simple Mendelian ratios.

Things to consider:


Understand what the question is asking before you answer it.

Relate answer to Mendelian ratios.

Sex linkage refers to the inheritance patterns determined by genes located on the sex chromosomes in humans. In females their chromosomes are in the combination of X and X. Males on the other hand carry an X and Y chromosome. The Y chromosome determines that the offspring is a male. The Y chromosome also carries very few genes. This causes in most cases, male offspring to inherit a sex linked trait due to the fact that it will only take one recessive gene from the mother to be expressed in the male offspring. This is evident in the sex linked disease colour blindness. For example if normal vision is represented by N and colour blindness is represented by n we can illustrate how this condition is sex linked.e.g. A heterozygous female with a normal vision male.

XN Xn

XNXN XNXN Xn

YXN YXn Y

In the resultant offspring both females have normal vision, one male has normal vision and one male has colour blindness. This is largely due to the fact that Y chromosome does not carry genetic material and therefore is susceptible to inheriting characteristics from the mother.

Co dominance is the process by which both alleles are expressed which means neither are dominant over the other. These two alleles are expressed and are not blended. For example roan cattle is the result of both genes being expressed separately without blending. (White and red).

http://www.ccs.k12.in.us/chsteachers/BYost/Biology%20Notes/CH11notescoincompletedom_files/image004.jpgSex linkage and co dominance do not produce simple Mendelian ratios. This is largely due to the fact that Mendel started with pure breeding parents. Mendel then interbred the offspring which limited the genetic pool, causing a steady ratio of plants with certain characteristics. Ratios from other situations like sex linkage and co dominance will not conform to Mendels ratios because Mendel did not study these complicated forms of inheritance.

Describe the work of Morgan that led to the understanding of sex linkage.

Things to consider:


Ensure you learn Morgans work as scientists are constantly referred to in the HSC.

Morgan first discovered sex linkage through his work with the Drosophila fruit fly. Morgan had been breeding Drosophila and one day he noticed a male white eyed fly within the population of red eye Drosophilas. This was an odd characteristic as all Drosophilas were meant to have red eyes. Morgan investigated the problem further. He bred the male white eyed fly with a red eye female. The resultant offspring all had red eyes. Morgan then interbred the first generation of offspring. The resultant second generation contained white eyed Drosophilas. All of these offspring with white eyes were males. Morgan then hypothesised from these results that the white eye characteristic was sex limited. Morgan suggested that sex limited, characteristics were carried on the X chromosome by the female. The result from this experiment is known as sex linkage.

Explain the relationship between homozygous and heterozygous genotypes and the resulting phenotypes in examples of co dominance.

Things to consider:


Link answer to co dominance. Be succinct.

Firstly homozygous genotypes are expressed by either capital letters or lower case letters showing either dominant or recessive genes. In comparison heterozygous genotypes are expressed by a capital and lower case letter.

Homozygous and heterozygous genotypes play an important role in co dominance. As we know co dominance means that both genes are expressed but not blended. For example, lets use AR for red flowers and AW. The results of a punnet square cross for these flowers would be:

ARAR

AWAR AWAR AW

AWAR AWAR AW

As indicated by the punnet square above the first generation (F1) of flowers all have the genotype AR AW. This means that the phenotype for these flowers is pink. If we cross the F1 generation using the above combinations the results are as follows:AR AW

ARAR ARAR AW

AWAR AWAW AW

As indicated by the punnet square above the second generation (F2) of flowers have the following varying genotypes and phenotypes of AR AR (red) AR AW (pink) and AW AW (white).

The above results still show that Mendels rules for inheritance still apply. This is because both alleles are expressed in the heterozygous manner and are both represented by their respective capital letters.

Outline ways in which the environment may affect the expression of a gene in an individual.

Things to consider:


Relate environment to gene expression.

There are many underlying principles that determine the phenotype of any individual. Our physical characteristics are not merely based on inheritance. The environment in which we live has a determining factor on what genes are expressed and why they are expressed. For example two people with the same genetic inheritance for tallness may not be the same height. These factors are somewhat regulated by the environment in which we live. Environmental factors can include such lifestyle choices such as nutrition. For example a person may have genetically inherited a gene for lean muscle, if this person changed their nutritional requirements and increased the amount of exercise in their life there is no reason why genes would not be expressed in a different manner in order for that person to gain bulk muscle. Another environmental factor that causes changes in genetic expression is geographic location. For example, a boy from Sydney and a boy from North Africa. These boys live in complete differing environments. The boy from Sydney is generally going to express genes for medium bones and strong muscles whereas the boy from North Africa is generally going to express genes for long bones and less muscle.

Overall the environment has a determining factor in the expression of genes.

Process information from secondary sources to construct a model that demonstrates meiosis and the process of crossing over, segregation of chromosomes and the production of haploid gametes.

Things to consider:

What does process and construct mean?

Identify the stages in which crossing over occurs, segregation of chromosomes occurs and the production of haploid gametes.

To complete the dot point accurately and efficiently you must complete the following tasks: read through the information for Modelling meiosis on page 166. Once you have completed the readings construct a diagram of the process of meiosis. Finally answer questions on Student Resource CD.Solve problems involving co dominance and sex linkage (Questions 1 9 p. 181 182 of text.)Things to consider:

- What does solve mean?

- What is co dominance?

- What is sex linkage?

Identify data sources and perform a first hand investigation to demonstrate the effect of environment on phenotype.

Things to consider:


What is phenotype?

Ensure you perform an accurate and reliable experiment and record all relevant results.

For example, we constructed an experiment involving tomato plants. These plants were placed in 3 environments. Environment 1 the plant was placed in the garden. Environment 2 the plant was placed in the house. Environment 3 the plant was placed in the garden shed. All the plants received 20mL of water per day. As environment 1 was outside it also received water in the form of rain.

Your task:

Describe the physical appearance of each plant and relate this to the environment in which the plant was exposed to. Suggested activity is to observe the effect of light on the growth of plants. Start by watching Clickview: The Scientific Method (15 mins). Design an experiment to test the hypothesis plants need light to grow.

Describe the process of DNA replication and explain its significance.Things to consider:

What does describe and explain mean?

Be succinct.

DNA is unique in the sense that it is the building blocks of all life forms but it is also capable of replicating itself exactly. This is possible because of the double helix structure being able to unwind. The process of DNA replication or copying takes place in meiosis and mitosis.

The process of DNA replication is outlined below: DNA replication begins with the two strands separating. The bonds break between the bases so that the two strands of DNA unzip. (Binding proteins prevent the strands from reattaching to one another)

A complimentary copy of each strand is constructed from new sugar phosphate base units. This process is catalysed by the enzyme DNA polymerase.

So in a brief summary; the DNA molecule unzips, a complimentary strand is produced, these two strands come together to form a new molecule of DNA.

This process is significant as DNA is the building blocks of life. Being able to replicate DNA means our body can repair itself when it is damaged (mitosis) or variation within a species (meiosis).

Outline, using a simple model, the process by which DNA controls the production of polypeptides.

Things to consider:


Underline key words

Be succinct

Polypeptides:

Is a chain or link of amino acids.

DNA controls the production of polypeptides in a process known as protein synthesis. This involves the following steps:

A gene on the DNA strand contains information required to build that specific polypeptide. This is in the form of a specific codon. (3 base sequence.)

Messenger RNA (mRNA) a special type of RNA carries the information from the DNA in the nucleus, to the ribosomes in the cytoplasm.

Transfer RNA (tRNA) brings amino acids to the ribosomes to help build the polypeptide. There are over 20 types of tRNA each carrying a different type of amino acid. Each tRNA contains complimentary bases to that of the mRNA.

Ribosomes act as the site for the synthesis of polypeptides. Ribosomes contain three active sites, one site to hold the mRNA strand and the other two for the tRNA. These sites temporarily bind these molecules in order for amino acids to link up and produce a polypeptide chain.

Enzymes also aid in catalysing the process. (Speed it up.)

Explain the relationship between polypeptides and proteins.

Things to consider:


Illustrate your answer by showing how polypeptides relate to proteins.

Proteins are large complex molecules which contain carbon, hydrogen, oxygen and nitrogen. These large complex molecules are made up of smaller molecules called amino acids. Amino acids are the building blocks of all proteins. There are only twenty known types of amino acids. These amino acids are linked by peptide bonds eventuating into a polypeptide bond. (POLY = many)

Explain how mutations in DNA may lead to the generation of new alleles.

Things to consider:


Refer answer to DNA and alleles.

Mutations in DNA can lead to the generation of new alleles. Firstly a mutation is a change in a gene. It is an alteration in the DNA of a certain gene. It may be a substitution whereby a base is substituted for another base. It may be a deletion whereby a whole base or bases are deleted completely from the sequence or it could be an insertion where an extra base or bases are added to the sequence. If this mutation takes place in a specific location on the gene it may alter the production of a specific protein. This alteration also effects the production of polypeptides, which in turn affects the gene. An example of a mutation that occurs in humans is sickle cell anaemia. This mutation occurs when there is one substitution in the DNA sequence resulting in the disease.

Mutations cause variation within an organism. Mutations may lead to the generation of new alleles in an organism. This would result in changes to the information carried by the DNA on the chromosome. Most mutations are lethal and the cell ultimately dies. However if the cell survives it increases the variation within a population of organisms. Mutation can occur during meiosis, consequently the mutation gets passed on from the parents to the offspring. Therefore it is evident that mutations can lead to the generation of new alleles.

Discuss evidence for the mutagenic nature of radiation.

Things to consider:

What does discuss mean?

Ensure you support your answer with relevant cases as well as statistics.

Mutagen Environmental factors that induce mutation.

During the 20th century there has been increasing evidence to suggest that radiation has mutagenic qualities. For example ultraviolet radiation from the sun, ionising radiation from atomic bombs (Hiroshima), nuclear accidents (Chernobyl) and simple x rays have all been linked to causing mutations within a population.

Sunlight is a known mutagen. U.V. light causes a deletion of certain bases in the DNA strand. Another known effect is that thymine bases begin to link together. This subsequently causes the DNA not to replicate and the cell to die. Mutation rates such as skin cancers have increased over the years due to the increase in U.V. light. It is known that due to an increase in pollution the hole in the ozone is getting larger. This has led to a higher rate of skin cancers in those people who are regularly exposed to U.V. light.

Atomic bombs such as the one in Hiroshima have shown the mutagenic nature of radiation. The ionising radiation in atomic bombs can break strands of DNA or even whole chromosomes. The atomic bomb of Hiroshima supports the mutagenic nature of radiation as many people died from leukaemia from years following the attack as well as descendents of people effected have displayed mutations.

The Chernobyl disaster of 1986 caused many deaths. However the full extent of the disaster has not been fully realised. Over 9 million people have been exposed to the radiation through food, soil and water contamination. It is believed that the life span of the people in the area will dramatically drop due to radiation induced cancers. The effects of the disaster can also be seen in that in every 3 calves that were born in the area 2 were still born. (First 5 years.)

X rays have also been linked with causing mutations within patients. In the 1950 and 1960s X rays were used to measure feet, resulting in early induced cancers. Nowadays X rays are only used under strict circumstances by doctors, dentists and scientists.

Explain how an understanding of the source of variation in organisms has provided support for Darwins theory of evolution by natural selection. (Page 213)

Things to consider:


Relate source of variation to Darwins theory of evolution.

Be succinct.

Firstly Darwins theory of evolution by natural selection states that organisms may vary according to changes in their physical environment. Through Darwins research he knew that certain desirable characteristics were passed on from one generation to the next however he did not know how these characteristics were passed on. Mendel showed how genes were passed on from generation to generation. Boveri and Sutton outlined how genes and chromosomes interacted and how they could be inherited. Then through the work of Watson and Crick the DNA molecule was discovered. Darwin knew that variation within a species was essential for natural selection to occur. The source of this variation is caused by changes in DNA eventually resulting in variation within the species.

Describe the concept of punctuated equilibrium in evolution and how it differs from the gradual process proposed by Darwin. (Page 134)

Things to consider:


You will have to define punctuated equilibrium.

Show the difference in your answer.

Punctuated equilibrium is the process by which an organism rapidly undergoes evolution followed by a period of stasis (no change/lull). This theory was proposed by Gould and Eldredge. Gould and Eldredges theory suggests that when a sudden change occurs in their environment the organism either moves out of the area or dies out. Populations on the edge of their niche may survive the sudden change in the environment. This species then evolve and migrate over time and then suddenly appear on the fossil record. This theory of evolution differs from Darwins theory of evolution as Darwin stated that evolution is a gradual process that takes millions of years.

Perform a first-hand investigation or process information from secondary sources to develop a simple model for polypeptide synthesis.

Things to consider:

As this is a choice between first hand or second hand we will be completing this as a secondary source activity.

What does process and develop mean?

Although notes are in detail make sure you keep your answer simple enough to understand it.

Polypeptide synthesis is the process undertaken by the DNA molecule to manufacture (make) certain proteins. There are two main steps involved in this process and they are outlined as follows:

Transcription (Copying phase) The DNA strand unwinds in the area of the gene that contains the information about the protein that is going to be made.

RNA polymerase moves along the DNA strand linking complimentary bases of RNA with the DNA to form the mRNA strand.

The start and stop codon limit the length of the mRNA strand.

Once this process is complete the mRNA strand is modified to only contain exons which are sections that only contain information to code for particular proteins. (Introns are spliced out.)

mRNA then moves from the nucleus to the cytoplasm.

Amino acids

Amino acids become active in the cytoplasm by an enzyme and begin to attach themselves to specific tRNA.

Translation (Change language)

mRNA binds to ribosome with the start codon AUG

tRNA carrying specific amino acid at one end and the anticodon at the other binds to the mRNA on the ribosome.

A second tRNA binds to the next codon linking with the first amino acid making a peptide bond.

First tRNA is removed from the ribosome.

Ribosome moves along mRNA strand one codon at a time.

Two tRNAs bound to the ribosome at any one time and their two amino acids are linked together. Subsequently a polypeptide forms.

When the stop codon is reached synthesis stops.

Polypeptide is then released into the cytoplasm. http://www.dnaftb.org/dnaftb/21/concept/index.htmlhttp://www.accessexcellence.org/RC/VL/GG/protein_synthesis.htmlhttp://www.youtube.com/watch?v=NJxobgkPEAoAnalyse information from secondary sources to outline the evidence that led to Beadle and Tatums one gene one protein hypothesis and to explain why this was altered to the one gene one polypeptide hypothesis. (Page 314/Internet)Things to consider:

What does analyse, outline and explain mean?

There are two parts to this answer. Ensure you explain why their hypothesis was changed.

The following evidence supports Beadle and Tatums one gene one polypeptide, hypothesis:

Beadle and Tatum performed their experiments on bread mould (Neurospora)

The bread mould was grown on a medium of sugar, salts and the vitamin biotin. These were the minimal requirements for the bread mould to grow. (Minimal medium.) They suggested that these substances must be converted by the mould into amino acids and that enzymes were responsible for this metabolism. To test this Beadle and Tatum exposed the spores to X rays to cause mutations. They then grew the mould on the minimal medium. If it grew it was discarded if it did not grow it was kept for further testing. The mould that did not grow was then exposed to a variety of media containing a different amino acid. They found that if they supplemented the minimal medium with a particular amino acid the mould would grow. This suggested that the mutants had lost the ability to produce particular amino acids because they lacked certain enzymes. This means that a mutant that required tyrosine to grow lacked the enzyme tyrosine. From this experiment Beadle and Tatum hypothesised that each gene coded for a particular enzyme, which was firstly known as the one gene one enzyme theory. The theory was changed to one gene one polypeptide because genes code for proteins and not enzymes, many proteins are made of more then one polypeptide and each gene codes for a polypeptide.Process information to construct a flow chart that shows that changes in DNA sequences can result in changes in cell activity (Internet)

Things to consider:

What does process and construct mean?

Explain the flow chart so it makes more sense to you.

Changes in the DNA sequence can result in changes in cell activity. For example if there is a substitution, insertion or deletion of a certain base sequence this can and will change cell activity. This is due to the fact that the change in the DNA sequence changes the whole process of transcription and translation. A change in a base is ultimately going to change the mRNA strand, the amino acid and the polypeptide. The flowchart below shows the result when thymine is deleted from the DNA strand. The deletion of thymine results in a premature stop in the formation of the amino acid.

(http://hsc.csu.edu.au/biology/core/blueprint/9_3_2/BIO934NET.htm#net10)

Cell activity, as we have learnt is regulated by enzymes. As indicated by the flow chart above a change in the DNA sequence also effects the formation of a functional enzyme.

Process and analyse information from secondary sources to explain a modern example of natural selection (Internet peppered moth)

Things to consider:

What does process, analyse and explain mean?

We have learnt about peppered moths before so you should have some understanding on this topic.

There are three main examples which you could use to answer this question:

Peppered moths

Mosquitoes (DDT) BacteriaPeppered Moths There were two observed varieties of peppered moths located in industrial England, black and white in colour. The white moths were much more common as they were well camouflaged by the lichen on the surrounding trees. As industry within the area developed in the 19th century soot began to build up on the trees and turn their bark a darker colour. This resulted in the white moths being eaten by birds while the black moths began to reproduce at a higher rate to pass on their desired characteristics. This example of natural selection was easily observable as it occurred over a relatively short period of time.

Mosquitoes (DDT) DDT was initially used to kill off insects and mosquitoes which affected crops and the production of food. It was initially a very successful insecticide until a small population of mosquitoes survived. These mosquitoes then passed on their immunity to the DDT onto further generations. This form of modern natural selection was easily observed as mosquitoes have a high reproduction rate. When the immunity is passed on it generates into millions of mosquitoes becoming resistant to DDT.

Bacteria Bacteria much like mosquitoes have become resistant to antibiotics. This is due to the fact that antibiotics are over prescribed or the patient does not complete the course of antibiotics. Much like the mosquitoes the bacteria that survive the chemicals in the antibiotics reproduce. Their desirable immunity is passed on from generation to generation resulting in the antibiotic have little to no effect on the bacteria. This is an example of modern day natural selection as it is easily observable in patients as well as the fact that scientists/doctors are constantly upgrading different antibiotics to become effective in the fight against resistant bacteria.

Process information from secondary sources to describe and analyse the relative importance of the work of:

James Watson

Francis Crick

Rosalind Franklin

Maurice Wilkins in determining the structure of DNA and the impact of the quality of collaboration and communication on their scientific research. (Internet research, page 192 - 194). DVD Secret of Photo 51: History of Rosalind Franklin and the Double Helix (52mins) Excellent!Things to consider:

What does process, describe and analyse mean?

Ensure you can link their work to current technologies that involve DNA.

Learn these scientists and their names as scientists are regularly tested on in the HSC.

James Watson, Francis Crick, Rosalind Franklin and Maurice Wilkins all played a pivotal role in determining the structure of the DNA molecule. However it has been publicised that they did not all work together cooperatively and there is still some debate over who should be accredited with the discovery of the DNA double helix.

Watson and Crick both had a passion for science, in particular the DNA molecule. They began their research together at Cambridge University in England. They bonded almost straight away and became a formidable research team. In contrast Rosalind Franklin and Maurice Wilkins were also researching the structure of DNA. Unlike Watson and Crick these two scientists did not get along. They despised each other. Watson and Crick also admitted to having a patronising attitude towards her. This was largely due to the fact that Rosalind Franklin was a female in a male dominated area of work. Franklin had few opportunities to express her ideas and to develop a positive working relationship with Wilkins.

Watson and Crick worked together as a team. They used the ideas of other scientists to solve the puzzle that was DNA. Ideas from other scientists that manipulated Watson and Cricks ideas included:

Linus Pauling showed that proteins are arranged in a shape of spring coil.

A talk by Franklin in 1951 illustrating DNA images produced by X ray crystallography initially causing Watson and Crick to produce an inaccurate model of DNA.

Erwin Chargaffs work on nitrogen bases enabled Crick to suggest that these nitrogen bases were complimentary to one another (A T, C G). This was firstly rejected by Watson until he came up with the idea that these pairs might be the rungs of the ladder.

While Watson and Crick were manipulating their ideas surrounding the structure of DNA, Franklin had discovered from her X ray diffraction pictures the double helix nature of DNA in 1953. However, Franklin did not announce her findings. Unknown to Franklin, Wilkins shared these images with Watson and Crick showing the structure of the DNA molecule. Subsequently Watson and Crick produced a 3 D model of the DNA structure as well as a theory surrounding the DNA double helix. In 1962 Watson, Crick and Wilkins were all accredited in determining the structure of DNA and were awarded the Nobel Prize.

Ultimately Watson and Crick are the two main scientists accredited to discovering the DNA structure.

Identify how the following current reproductive techniques may alter the genetic composition of a population: (pages 218 to 223)

artificial insemination

artificial pollination

cloning

Things to consider:


Address each heading.

Be succinct

Artificial Insemination is the process by which sperm is collected and inserted into the vagina of the female. The sperm then swim to the egg, which becomes fertilised. Artificial insemination has the potential to alter the genetic composition of a population. If the same female or same male is constantly being used this may limit the genetic variability of the population. This then decreases biodiversity within the population increasing the susceptibility of the population to disease and infection. Artificial insemination could also be beneficial for the population as desired characteristics are the main reason for artificial insemination. These desired characteristics could enable the population to be strong, fit and healthy.

Artificial Pollination is a similar process to that of artificial insemination but this time with plants. The plant breeder will brush the pollen from the anther (male) onto the stigma (female). The plant is then covered to prevent cross pollination. This results in the desired plant to grow. This reproductive technique may alter the genetic composition of the population in many ways. Firstly it will affect the genetic diversity of the plant. Secondly this will affect the biodiversity of the plant and thirdly if the plant is susceptible to a specific disease as all plants are alike they have the potential to be wiped out.

Cloning is the process in which an exact copy is made of an organism (Dolly). Cloning can have an adverse affect on a population. As clones are exacts copies of one another there is a total lack of genetic variation. If a disease kills one clone it will more then likely kill the rest of the population. Cloning lacks total genetic variation and biodiversity.

Outline the processes used to produce transgenic species and include examples of this process and reasons for its use. (pages 225 to 230)

Things to consider:


What are transgenic species?

State examples

A transgenic organism is an organism that has had a new piece of DNA spliced into a chromosome in each of its cells. This new piece of DNA is usually inserted to produce a new type of protein for that type of organism. The new piece of DNA may come from a totally different species or a different organism within the same species.

The production of a transgenic species involves the following steps:

The useful gene and the chromosome it is one are identified.

The gene is isolated and is cut off from its DNA strand. Separate DNA sequences are added to the sequence to ensure the gene will work. (This step may not be necessary) Multiple copies of the gene are made. (Not in all cases) The gene is inserted into the cell of another organism. Once inserted the gene must become part of the genetic material of that organism. The organism is not a transgenic species unless it is able to pass that specific gene on from generation to generation. This desired gene needs to be expressed.An example of a transgenic species within Australia is the production of sheep with superior wool. Through research scientists have discovered that cysteine is responsible for the production of superior wool. Scientists are developing this transgenic species by inserting the gene responsible for producing cysteine into sheep. Once this gene is introduced into the sheeps egg, the sheep grows, producing premium wool as well as breeding and passing on the desired gene onto the next generation.

Discuss the potential impact of the use of reproduction technologies on the genetic diversity of species using a named plant and animal example that have been genetically altered. (pages 232 235)

Things to consider:

What do the terms discuss and impact mean? What is genetic diversity? Will it lack or improve?Reproductive technologies can have a positive and negative affect on the diversity of species. For example in Australia new varieties of tomatoes have been genetically altered to have a longer shelf life and a greater taste. This in a sense is a positive because if the tomatoes are a success in the market place they will continue to be genetically engineered while other tomatoes will be discarded. This in turn produces a larger yield of tomatoes for the farmer. The negatives for the production of these tomatoes are that they are all genetically similar. This in turn limits genetic variation within a population of the tomatoes. This also makes the crop susceptible to disease, which in turn could wipe out a whole crop. Tomatoes that are not genetically modified have a greater chance of spreading their desired characteristics from one generation to the next.

An animal example that has been genetically modified is transgenic sheep. These sheep have had cysteine inserted into their egg, this egg develops into a sheep, which produces high quality wool and the cysteine gene is passed on from generation to generation. Once again a positive for the development of this species is that high quality wool is being produced for the market place. The negatives for this transgenic species are that there is a lack of genetic variation within the population causing a lack of diversity. This species maybe susceptible to disease causing a decrease in wool production and the loss of money.

Process information from secondary sources to describe a methodology used in cloning. (Pages 223 to 225, Student Resource CD and internet research)

Things to consider:

What does process and describe mean?

What is cloning? List the steps involved.The following is the methodology in cloning Dolly the sheep:

Extracted an egg cell from a female sheep and destroyed the nucleus.

Mammary cells were taken from a donor ewe.

The nucleus from the mammary cell was inserted into the egg which lacked a nucleus.

The egg with a new nucleus developed into a sheep.

This sheep had exactly the same genetic make up as that of the donor ewe. (Mammary cell.)

The above process was the simple process in order to clone Dolly the sheep. However it was not as simple as outlined above. Scientists encountered many mutations and premature deaths of the developing sheep. It took years to develop and clone Dolly the sheep.

Analyse information from secondary sources to identify examples of the use of transgenic species and use available evidence to debate the ethical issues arising from the development and use of transgenic species. (pages 230 to 232, Student Resource CD and internet research)

What does analyse and identify mean?

Be succinct. It is also valuable to contain some information about the ethical issues so that you have that background knowledge.

Some examples of transgenic species are:

Sheep are injected with a gene responsible for producing a clotting factor in their milk. This clotting factor is administered to humans who suffer from haemophilia.

In Scandinavia farmers are able to grow strawberries in the cold climate by splicing a gene from the salmon into their DNA so they can tolerate cold temperatures. Scientists have genetically altered alfalfa so it produces higher cysteine levels. These higher cysteine levels enable sheep that graze on the alfalfa to produce higher quality wool. Scientists have also spliced cysteine into a sheeps egg. This egg in turn develops into a sheep, which expresses the gene, which in turn produces premium wool. This gene is desirable and is passed on from generation to generation.Above are some examples of what transgenic species are used for. However there are many social, economic and ethical implications that arise from the use of these new reproductive technologies. The issues are as follows:

Food Safety and Health:

Are the genetically altered plants and animals safe to eat?

Has any of the nutritional information of the genetically altered plant and animal been changed in any way for the good or the bad?Environmental Protection:

What effect could the genetically altered organism have on the natural ecosystem?

Could the genetically altered organism cause damage to the surrounding ecosystem? Could the genetically altered organism reproduce uncontrollably? Could there be a decrease in the biodiversity of the genetically altered organism?Regulating Issues:

Should the government produce certain regulations to protect farmers, consumers and environment?

Should genetically modified foods be labelled or easily identified in the supermarket?

Social and Economic Effects:

What effect would genetically modified organisms have on farming practices?

Could biotechnology companies eventually take over farming and have patents and copyrights on the production of certain genetically modified organisms? This in turn would mean that these groups would control world food production.

Could the money spent on genetic engineering be spent on something more practical such as human health, housing and nutrition?

Ethical and Moral Issues:

Why should we stop the production of these organisms if they help cure/aid in the prevention of disease?

Why should we stop the production of these organisms if they increase the production of food?

Should we tamper with the process of evolution?

Should we change the genetics of an organism for commercial gain?

The above issues are slight indications on the effect transgenic species have on people today. People will be in constant debate on the benefits of transgenic species.