2 nd Semester EOC Review Meiosis Used to create Sex Cells – GametesUsed to create Sex Cells – Gametes 2 Distinct Division2 Distinct Division –Meiosis.

2nd Semester EOC Review

MeiosisMeiosis

• Used to create Sex Cells – GametesUsed to create Sex Cells – Gametes

• 2 Distinct Division2 Distinct Division– Meiosis I – Meiosis I –

• separation of homologous chromosomesseparation of homologous chromosomes

– Meiosis II – Meiosis II – • separation of sister chromatidsseparation of sister chromatids

• 8 phases8 phases

**Label the following diagramLabel the following diagram

Define the following terms

• Allele

• Genotype

• Phenotype

• Autosomes

• Sex Chromosomes

Define the following terms

• Allele- an alternative form of a gene

• Genotype-the genetic makeup of an individual

• Phenotype-the physical appearance of an individual

• Autosomes-body chromosomes

• Sex chromosomes: xx or xy to denote male or female

Mendel’s LawsMendel’s Laws

• Name and define the 4 LawsName and define the 4 Laws• Law of Segregation: Chromosomes Law of Segregation: Chromosomes

separate during meiosisseparate during meiosis• Law of Independent Assortment: Separate Law of Independent Assortment: Separate

independently of each other.independently of each other.• Law of Dominance: dominant trait can Law of Dominance: dominant trait can

mask (hide) the recessive.mask (hide) the recessive.• Law of Unit Factors: each trait has two Law of Unit Factors: each trait has two

factors that apply to the genotypefactors that apply to the genotype

Segregation

Mendel studied genes that:1. Typically possess two alleles--one

dominant and one recessive. (e.g. G, g).2. Exhibit complete dominance. (e.g., green peas are GG or Gg)3. Do not have effects on viability

or survival rates of the progeny. (e.g. Peas with green or yellow

seeds grow and survive equally well)

Tools to predict OffspringTools to predict Offspring

• What tools are used to predict offspring What tools are used to predict offspring possibilities?possibilities?

• PedigreePedigree– Used to look at ancestors of organisms now aliveUsed to look at ancestors of organisms now alive

• Punnett Squares Punnett Squares – Used to predict future offspring from known parentsUsed to predict future offspring from known parents

• TestcrossTestcross– Used to identify unknown genotypes of current Used to identify unknown genotypes of current

organismsorganisms– Breeding.Breeding.

Pedigree analysis

Some single gene traits in Humans

Polydactly (dominant)

Widow’s peak (dominant)

Albinism (recessive)

Sickle cell anemia (partiallyrecessive)

Punnett SquaresPunnett Squares

• MonohybridMonohybrid– Dealing with only one traitDealing with only one trait– Tall vs shortTall vs short

• DihybridDihybrid– Dealing with two traitsDealing with two traits

• Key TermsKey Terms– Homozygous = purebred = same allelesHomozygous = purebred = same alleles– Heterozygous = hybrid = different allelesHeterozygous = hybrid = different alleles

Complex TraitsComplex Traits

• Incomplete DominantIncomplete Dominant

• CodominantCodominant

• Sex LinkedSex Linked

• Multiple PhenotypesMultiple Phenotypes

• Multiple GenesMultiple Genes

*Describe each of these complex *Describe each of these complex traitstraits

Incomplete Dominance

1. Normal dominance: The heterozygote genotype Aa has the same phenotype as the homozygote genotype AA.

2. Incomplete dominance: The heterozygote genotype Aa has a different phenotype from that of the homozygote genotype AA, typically intermediate between AA and aa.

CodominanceCodominance

• The heterozygote The heterozygote genotype Aa genotype Aa expresses two expresses two different phenotypes different phenotypes at the same time.at the same time.

• Ex. Checkered Ex. Checkered chicken chicken

3. Codominance: In sickle cell anemia, the two alleles HbS and HbA produce different types of hemoglobin.

These hemoglobins can be “visualized” using protein electrophoresis:

normal

sickled

Cell shape

Sex Chromosomes and Sex Determination

X and Y chromosomes are found on the 23rd pair in humans. They determine sex of the organism. XX = female XY = male. Some genetic disorders are found on the X chromosome. Most of these are recessive therefore the girls can hide them (carriers). Most sex-linked genetic disorders are expressed in males since they only have one x chromosome.

Sex-linked inheritance: A demonstration

Multiple AllelesMultiple Alleles

• Some traits use multiple alleles to code for Some traits use multiple alleles to code for a trait. This allows for many combinations a trait. This allows for many combinations and therefore many different phenotypes and therefore many different phenotypes to be expressed.to be expressed.– Remember each organism has only two of Remember each organism has only two of

these options per trait.these options per trait.– Blood Type – IBlood Type – IAA, I, IBB, i, i

ABO blood typing system in humans

Multiple alleles: A, B, O

A > O (A dominant to O)B > O (B dominant to O)A = B (A, B codominant)

Multiple GenesMultiple Genes

• These are hard to These are hard to predictpredict

• Examples include: Examples include: height, hair color, eye height, hair color, eye colorcolor

Issues with MeiosisIssues with Meiosis

• What is nondisjunction and what are What is nondisjunction and what are the possible results?the possible results?

• Nondisjunction is the failure of Nondisjunction is the failure of chromosomes to separate chromosomes to separate during anaphase I or II of during anaphase I or II of meiosis.meiosis.

Karyotype is a tool used for identifying Karyotype is a tool used for identifying nondisjunctionnondisjunction

Nondisjunction of chromosomes

What is it?

Ordinarily homologouschromosomes separateat Meiosis I and II.

If this does not occur,then gametes canend up with twohomologous chromosomes

Down Syndrome ~ NondisjunctionDown Syndrome ~ Nondisjunction

• Caused by an extra Caused by an extra 21st chromosome. 21st chromosome.

• Hence the scientific Hence the scientific name, Trisomy 21. name, Trisomy 21.

MutationsMutations

• 2 Different levels2 Different levels– Gene – affects entire geneGene – affects entire gene

• What are the 4 gene mutations ?What are the 4 gene mutations ?• Deletion, insertion, translocation, inversionDeletion, insertion, translocation, inversion• What are the 2 nucleotide mutations?What are the 2 nucleotide mutations?

– nucleotide – affect one nucleotide (A, T, C, nucleotide – affect one nucleotide (A, T, C, G’s)G’s)• Points & frameshiftPoints & frameshift

Variation Caused By MeiosisVariation Caused By Meiosis

• How can variation increase in a How can variation increase in a population?population?

• Called Meiotic (genetic) RecombinationCalled Meiotic (genetic) Recombination1.1. Many different gamete possibilities (2Many different gamete possibilities (2nn) – ) –

random assortmentrandom assortment2.2. Crossing over – during Prophase I some of Crossing over – during Prophase I some of

the genes swap homologous chromosomesthe genes swap homologous chromosomes3.3. Fertilization – one gamete with anotherFertilization – one gamete with another4.4. MutationsMutations

DNA Structure and Function

DNA Structure

• What are the three parts of DNA?

DNA Structure

• What are 4 different DNA nucleotides and how do they combine?

DNA Replication

• What is DNA replication?• Replication = identical new strand

– Happens for cell division – either mitosis or meiosis.

• What are the steps of replication?– 1. Enzyme unzips DNA molecule– 2. Free nucleotides come bind with

complimentary base pairs– 3. Backbone forms by nucleotides bonding

DNA Function

DNA Function

• What are the two steps of protein synthesis?– 1. In nucleus – TRANSCRIPTION = forming

RNA strands– 2. In cytoplasm with a ribosome –

TRANSLATION = coding for amino acid chains = proteins

Transcription

• Describe each type of RNA?• Ribosomal RNA – rRNA: production of

ribosome• Transfer RNA – tRNA: bring Amino Acids to

ribosome for connection• Messenger RNA – mRNA: transfers code from

DNA in nucleus to ribosome for correct amino acid sequence.

Transcription

• How RNA is different from DNA?

– 1. Single Stranded

– 2. Ribose instead of Deoxyribose

– 3. Uracil instead of Thymine

– 4. Can leave nucleus

Transcription

• Process of making mRNA which is a “copying” the DNA code.

• Each mRNA is made from a series of DNA nucleotides which code for one Gene (trait).– Codes only one side of the DNA

• The mRNA can then leave the nucleus for protein formation.

Transcription

• Describe the steps of transcription.– 1. Enzyme unzips DNA at gene location– 2. Free RNA nucleotides match up to their

complimentary bases on DNA• DNA RNA

A U

T A

C G

G C

– 3. RNA breaks off and leaves nucleus

Translation

• Describe the steps of translation.

• mRNA attaches to a Ribosome in cytoplasm.

• The code is read by the ribosome in a series of 3 nucleotides (aka triplicate) – called a codon.

Translation – mRNA code

Translation

• Each codon codes for one amino acid– 3 RNA nucleotides = 1 amino acid– 1 codon = 1 amino acid– 9 nucleotides =_?_Codons = _?_ Amino acids

• tRNA match up to codons using anticodons. • Each tRNA brings 1 amino acid to the mRNA for

attachment.• Amino Acids connect together to form proteins.

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Evolution History & Natural Selection

Answer the following questions

• List the 4 basic principles of natural selection.

• Identify what each of the following scientists did:– Malthus, Lamarck, Wallace, and Darwin

• Which scientist’s theory is no longer accepted? Why?

• Which scientist is credited with the modern day theory of evolution?

Evolution

• Define evolution?

• The change in a population over time.–Must be Genetic

• Thought to be caused by natural selection

Important Scientists

• 1798 - Malthus – Essay on Population Control.

• 1809 – Lamarck – Use and Disuse (Has been DISPROVED!!!!!!)

• 1858- Wallace – coined Natural Selection

• 1858 – Darwin – Published Origin of Species.

Charles Darwin

• Naturalist• Sailed on the Beagle• Studied variation

– Galapagos Islands

• Continued his study & wrote Origin of Species– Book describing the

principles of Natural Selection.

Natural Selection• Define Natural Selection?• A change in the population that

occurs when organisms with favorable variations for a particular environment survive and pass on the trait to the next generation.

• Survival of the fittest

Which of these is the fittest?

– What does fittest mean?– Not Strongest

Natural Selection Principles:

1. There is a variation within the population.2. Some of the variations are favorable

– Allows organisms to survive better than others

3. There is a struggle for existence– More individuals are produced than live to

reproduce

4. Those that survive have the favorable variation and REPRODUCE.

– The next generation has the favorable trait• Traits are GENETIC = In DNA

Variations

• The differences between individual members of a population.

Variations• Favorable variations are caused by genetic

recombination.1. Crossing Over

2. Random Assortment of Homologous Chromosomes

3. Fertilization

4. Mutation

– Changes caused by mutations in DNA that allows the organism to better survive.

– Advantageous Mutations

Variations• When these variations occur there will

be more offspring from these organism because of the survival rate.

• This slowly changes the species over time.

–Based upon generational time.

Adaptations

• An inherited trait that increases a population’s chances of survival and reproduction in a particular environment

Adaptations• Types of adaptations

• Structural: Used for defense against predators

• Physiological: Changes in metabolic processes for survival.

Structural Adaptations

• Examples:

• Defense - Horn, Thorn, Armor, Poison

• Mimicry and Camouflage to hide

Physiological Adaptation

• Examples:

• Resistance to chemicals such as antibiotics.

• Pest resistance to pesticides

Classification

• Who is responsible for the modern system of classification?

• What is the proper way to write out scientific name?

• Write from broad to specific the order of classification.

List the following information for each of the 6 Kingdoms:

KingdomProkaryote or Eukaryote

Heterotroph, Autotroph or Both

Organisms found in the kingdom

Archaebacteria

Eubacteria

Protista

Fungi

Plantae

Animalia