4.4 genetic engineering & biotechnology

4.4 Genetic Engineering & Biotechnology

Topic 4 Genetics

Genetic Engineering 4.4.1 Outline the use of polymerase chain reaction (PCR)

to copy and amplify minute quantities of DNA. Details of methods are not required.

4.4.2 State that, in gel electrophoresis, fragments of DNA move in an electric field and are separated according to their size.

4.4.3 State that gel electrophoresis of DNA is used in DNA profiling.

4.4.4 Describe the application of DNA profiling to determine paternity and also in forensic investigations.

Genetic Engineering Aim 8: There is a variety of social implications stemming

from DNA profiling, such as identity issues for a child who learns unexpectedly who his or her biological father is, self-esteem problems for someone who learns he is not a father, problems in relationships where the male partner learns that he did not father a child, but also relief for crime victims when those responsible for the crime are identified and convicted, sometimes decades later.

Genetic Engineering TOK: A comparison could be made between blood groups

and DNA profiles in their potential for determining paternity. The difficulty in assessing the chance of two individuals having the same profile could be discussed, and also the success of DNA profiling in securing convictions in some of the high-profile legal cases of recent years.

Genetic Engineering 4.4.5 Analyse DNA profiles to draw conclusions about

paternity or forensic investigations. The outcomes of this analysis could include knowledge of

the number of human genes, the location of specific genes, discovery of proteins and their functions, and evolutionary relationships.

Aim 7: Online bioinformatics simulations are available.

Genetic Engineering Aim 8: We can either emphasize the large shared content

of the human genome, which is common to all of us and should give us a sense of unity, or we can emphasize the small but significant allelic differences that create the biodiversity within our species, which should be treasured. Differences in the success of human races in coping with the modern world and the threat to some small human tribes could be mentioned. It is important to stress parity of esteem of all humans, whatever their genome.

Genetic Engineering TOK: The Human Genome Project was an international

endeavour, with laboratories throughout the world collaborating. However, there were also efforts in some parts of the world to gain commercial benefits from the outcomes of the project.

The data from the Human Genome Project can be viewed in different ways: it could be seen as a complete account of what makes up a human, if one takes a reductionist view of life, or, alternatively, as merely the chemical instructions that have allowed a huge range of more significant human characteristics to develop. This could lead to a discussion about the essential nature of humanity.

Genetic Engineering 4.4.6 Outline three outcomes of the sequencing of the

complete human genome.

4.4.7 State that, when genes are transferred between species, the amino acid sequence of polypeptides translated from them is unchanged because the genetic code is universal.

Genetic Engineering Aim 8: There is an ethical or moral question here: whether

it is right to change the genetic integrity of a species by transferring genes to it from another species. The discussion could include the wider question of selective breeding of animals, and whether this is distinctively different and always acceptable. The possibility of animals suffering as a result of genetic modification could be considered.

Genetic Engineering 4.4.8 Outline a basic technique used for gene transfer

involving plasmids, a host cell (bacterium, yeast or other cell), restriction enzymes (endonucleases) and DNA ligase.

The use of E. coli in gene technology is well documented. Most of its DNA is in one circular chromosome, but it also has plasmids (smaller circles of DNA). These plasmids can be removed and cleaved by restriction enzymes at target sequences. DNA fragments from another organism can also be cleaved by the same restriction enzyme, and these pieces can be added to the open plasmid and spliced together by ligase. The recombinant plasmids formed can be inserted into new host cells and cloned.

Genetic Engineering 4.4.9 State two examples of the current uses of genetically

modified crops or animals. Examples include salt tolerance in tomato plants, synthesis of

beta-carotene (vitamin A precursor) in rice, herbicide resistance in crop plants and factor IX (human blood clotting) in sheep milk.

Aim 8: The economic benefits of genetic modification to biotechnology companies that perform it could be considered. Also mention the possibility that harmful changes to local economies could result, and the danger that wealth could become more concentrated in a smaller percentage of the population if expensive but profitable new techniques are introduced. In this respect, inequalities in wealth may become greater.

Genetic Engineering 4.4.10 Discuss the potential benefits and possible harmful

effects of one example of genetic modification. Aim 8: There are ethical questions here about how far it is

acceptable for humans to change other species, as well as other ecosystems, in order to gain benefit for humans.

Genetic Engineering TOK: This is an opportunity to discuss how we can assess

whether risks are great enough to justify banning techniques and how the scientific community can inform communities generally about potential risks. Informed decisions need to be made but irrational fears should not be propagated. Consideration could be given to the paradox that careful research is needed to assess the risks, but performing this research in itself could be risky. Do protesters who destroy trials of GM crops make the world safer?

Genetic Engineering 4.4.11 Define clone. Clone: a group of genetically identical organisms or a

group of cells derived from a single parent cell. 4.4.12 Outline a technique for cloning using differentiated

animal cells. Aim 8: Ethical questions about cloning should be

separated into questions about reproductive cloning and therapeutic cloning. Some groups are vehemently opposed to both types.

Genetic Engineering 4.4.13 Discuss the ethical issues of therapeutic cloning in

humans. Therapeutic cloning is the creation of an embryo to supply

embryonic stem cells for medical use.

Polymerase Chain Reaction (PCR) Sometimes you only have a very small sample of DNA. The polymerase chain reaction (PCR for short) can make

multiple copies of minute quantities of DNA very quickly. This process is done without the need of bacteria. The sample of DNA is repeatedly heated and cooled, in

the presence of an enzyme, DNA polymerase and nucleotides.

The heating opens the DNA double helix. The DNA polymerase attaches the nucleotides.

Polymerase Chain Reaction (PCR)

Ref: Advanced Biology, Kent

Gel Electrophoresis Gel Electrophoresis is a process used to separate

fragmented pieces of DNA according to their charge and size.

DNA is made up of a lot of repeated nucleotide sequences (junk DNA). Around 90% of our DNA is junk DNA.

The frequency of junk repeats is characteristic for an individual, just as fingerprints or iris patterns are unique.

This pattern enables the DNA to be exactly matched to a person.

Gel electrophoresis is used in DNA profiling.

Gel Electrophoresis DNA can be cut into lengths using restriction enzymes. This produces fragments called Restriction Fragment

Length Polymorphisms (RFLPs). DNA is negatively charged, so these fragments can be

separated in an electric field. The negatively charged fragments move towards the

anode (positive terminal). The smaller fragments move further than the larger ones. This produces a banding pattern, unique for each

individual.

Gel Electrophoresis

Ref: Biology, Campbell

Ref: Advanced Biology, Kent

Gel Electrophoresis can be used in criminal investigations

Gel Electrophoresis

DNA Profiling DNA profiling is sometimes called DNA fingerprinting. Gel electrophoresis can be used in DNA profiling. Two major uses of DNA profiling are:

Criminal investigations. Paternity testing.

The only major worry about the accuracy of DNA profiling is the risk of contamination of samples.

Genetic Screening Genetic screening is the testing of an individual for the

presence or absence of a gene. This can be used to test for certain diseases of which the

gene responsible is known. The question of whether genetic screening techniques

should be used in human populations has been widely discussed.

There are potential advantages but also possible disadvantages.

Advantages of Genetic Screening1. Fewer children with genetic diseases are born.

Men or women who are carriers of an allele that causes a genetic disease could avoid having children with the disease by choosing a partner who has been screened and found not to be a carrier of the same allele.

2. Frequency of alleles causing genetic disease can be reduced.Couples who know that they are both carriers of a recessive allele that causes a genetic disease could use IVF to produce embryos screened for the allele. Embryos that do not carry the allele could be used.

3. Genetic diseases can be found and treated more effectively.If some genetic diseases are diagnosed when a child is very young, treatments can be given which prevent some or all of the symptoms of the disease. PKU is an example of this.

Disadvantages of Genetic Screening1. Frequency of abortion may increase.

If a genetic disease is diagnosed in a child before birth, the parents may decide to have it aborted. Some people believe that this is unethical.

2. Harmful psychological effects.If a person discovers by genetic screening that they have a genetic disease or will develop a disease when they are older, this knowledge might cause the person to become depressed.

3. Creation of a genetic underclass.People who are found to have a genetic disease may be refused jobs, life insurance and health insurance and be less likely to find a partner.

The Human Genome Project (HGC) Genome: the complete set of genetic material of an

organism. Humans have about 30,000-40,000 genes It is estimated that there are about 3.3billion nucleotides

in the human genome. The human genome project is an international cooperative

venture to sequence the complete human genome. Many research groups around the world are working out

the nucleotide sequence of the different chromosomes, or parts of chromosomes.

It was started in 1990 and was originally estimated to take 15 years but was finished in 2003.

The Human Genome Project (HGC) There are possible advantageous outcomes from the

HGC: It should lead to the understanding of many genetic disorders.

We will be able to easily identify genes that cause genetic disorders and test people for them by making gene probes.

It will allow the production of new drugs based on DNA base sequences of genes or the structure of proteins coded for by these genes.

Research into a particular disease can now focus on only the gene (s) that are relevant to the disease.

It can provide more information about evolutionary paths by comparing similarities and differences in genes between species.

Genetic Engineering Genetic material can be transferred between species. This can occur because the genetic code is universal to

all living organisms. The process used to transfer genetic material is called

Genetic Engineering it is also known as Recombinant DNA technology.

For genetic engineering you need: The gene to be transferred from the donor organism. Restriction enzymes (restriction endonucleases). Ligase enzymes A host cell (usually a bacterium) and their plasmids (circular

rings of DNA.

Genetic Engineering Potential uses of genetic engineering fall into three

categories: To produce a protein product.

Human growth hormone. Endow a particular organism with a characteristic it did not

previously possess. Pest resistance in crops.

To create more copies of a gene. So it can be studied more.

Genetic Engineering The general steps in genetic engineering are:

Circular rings of DNA called plasmids are obtained from a bacterium (E. Coli is commonly used).

The plasmids are cut using a particular restriction enzyme leaving sticky ends on the plasmid.

The same restriction enzymes are used to cut the required gene from the donor organism, leaving the same sticky ends.

The gene and plasmids are combined and the gene is spliced into the plasmid using ligase enzymes.

The recombinant plasmid is reinserted into the bacterium and allowed to multiply.

Ref: Biology, Campbell

Ref: Biology for the IB Diploma, Allott

Genetically Modified Organisms Organisms that have had genes transferred to them are

called Genetically Modified Organisms (GMOs) or transgenic organisms.

Some examples of GMOs are: Herbicide resistance in crops. Sheep that produce human blood clotting factor IX. Salt tolerance in plants. Delayed ripening in tomatoes (Flavr-Savr™). Bacteria use to produce insulin and clotting factor VIII. Bt Corn resistant to insects.

Herbicide Resistance Herbicide resistance in crops:

Almost all plants are killed by the herbicide glyphosphate. A gene for resistance to glyphosphate was discovered in a

bacterium. This gene has been transferred to maize and other crops. The transgeneic crops can be sprayed with glyphosphate to kill

the weeds but not the crop.

Blood Clotting Factor IX in Sheep Sheep that produce human blood clotting factor IX.

A gene for the production of the human blood clotting factor IX was inserted into sheep.

They produce the clotting factor in their milk, which can be collected and the clotting factor extracted.

The clotting factor can be administrated to humans.

Gene Therapy Gene therapy is the treatment of genetic disorders by

altering the genome. Gene therapy involves the replacement of defective genes

with gene with the correct functioning alleles. Examples of where gene therapy has been tried include:

Treatment of cystic fibrosis Treatment of SCID (severe combined immune disorder). Treatment of thalassemia.

Benefits and harmful effects of Bt Corn Bt corn contains a gene from Bacillus thuringiensis which

produces a protein toxic to specific insects( European corn borer).

Benefits:1. Damage caused by insect reduced.2. More expensive, but the difference is less than one extra

application of insecticide.3. Non Bt corn needs to be checked often for signs of the

borer.4. Less insecticide needed means less impact on the

environment.5. Reduces the infection with fungus also.

HARMFUL EFFECTS OF Bt CORN1. Will also kill some other insects.2. Insects may develop resistance to Bt toxin because they

are exposed to it all the time.3. Insects also make Bt spray useless as insecticide( Bt spray

is safe for humans and environment)4. It is difficult to prevent pollent (with Bt gene) from

travelling outside the field where Bt corn is grown.-it may fertilise organically grown non Bt corn which can no

longer be sold as organic corn.- It may fertilise wild relatives and makethem more resistant

to insects and have them dominate the niche they live in resulting in loss of biodiversity.

Cloning Clone is a group of genetically identical

organisms or a group of cells artificially derived from a single parent.

The technique for cloning using differentiated cells is mostly somatic cell nuclear transfer but the use made of the produced cells can be quite different like reproductive and therapeutic cloning.

REPRODUCTIVE CLONING

Reproductive cloning creates a new individual( Dolly was the first cloned sheep).Cloning using differentiated cell.

Steps involved in reproductive cloning1. From the original donor sheep to be cloned, a somatic cell

(non-gamete cell) from the udder was collected and cultured. Nucleus was removed from the cultured cell.

2. An unfertilized egg was collected from another sheep and its nucleus was removed.

3. Using a zap of electric current, the egg cell and the nucleus from the cultured somatic cell were fused together.

4.The new cell developed in vitro in a similar way to a zygote and started to form an embryo.

5. The embryo was placed in a womb of surrogate mother sheep.

6. The embryo developed normally.7. Dolly was born, and was presented to the world as a clone

of the original donor sheep.

Therapeutic cloning (cloning using undifferentiated cells) In some cases, scientists are not interested in making an

organism but simply in making copies of cells. This is called therapeutic cloning.

In therapeutic cloning human embryos are produced, the cells are referred to as embryonic stem cells

Aim is to develop cells which have not yet gone through the process of differentiation.

The cells can grow into any of a large number of different specialised tissues.

This cloning aims at cell therapy where diseased cells are replaced with healthy cells.

Use of embryonic stem cells Growing skin to repair a serious burn. Growing new heart muscle to repair an

ailing heart. Growing new kidney tissue to rebuild a

failing kidney. Bone marrow transplants for patients with

leukemia.

Ethical Issues of therapeutic cloning in humans Arguments in favour of therapeutic cloning1. Ability to cure serious diseases with cell therapy,

currently leukemia and in the future possibly cancer and diabetes.

Arguments against therapeutic cloning1.Fears of it leading to reproductive cloning.2. Use of embryonic stem cells involves the creation and

destruction of human embryos3. Embryonic stem cells are capable of many divisions and

may turn into tumours.

IBO guide: 4.4.1 Outline the use of polymerase chain reaction (PCR)

to copy and amplify minute quantities of DNA. Details of methods are not required.

4.4.2 State that, in gel electrophoresis, fragments of DNA move in an electric field and are separated according to their size.

4.4.3 State that gel electrophoresis of DNA is used in DNA profiling.

4.4.4 Describe the application of DNA profiling to determine paternity and also in forensic investigations.

IBO guide: 4.4.5 Analyse DNA profiles to draw conclusions about

paternity or forensic investigations.

4.4.6 Outline three outcomes of the sequencing of the complete human genome.

4.4.7 State that, when genes are transferred between species, the amino acid sequence of polypeptides translated from them is unchanged because the genetic code is universal.

IBO guide: 4.4.8 Outline a basic technique used for gene transfer

involving plasmids, a host cell (bacterium, yeast or other cell), restriction enzymes (endonucleases) and DNA ligase.

4.4.9 State two examples of the current uses of genetically modified crops or animals.

4.4.10 Discuss the potential benefits and possible harmful effects of one example of genetic modification.

IBO guide: 4.4.11 Define clone. Clone: a group of genetically identical organisms or a

group of cells derived from a single parent cell. 4.4.12 Outline a technique for cloning using differentiated

animal cells. 4.4.13 Discuss the ethical issues of therapeutic cloning in

humans. Therapeutic cloning is the creation of an embryo to supply

embryonic stem cells for medical use.