Biology 205 Population Genetics

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I. Evolution: Darwin's Dangerous Idea.

A. Define the term evolution as used by biologists today.

• Modification with genealogy. All kinds of organisms linked by having a common ancestor.
• Change in the genetic make up of a population.

B. List Darwin's key ideas about evolution.

• Evolution is a population process.
• Heritable phenotypic variation is important.
• Those individuals that are best suited to a particular environment tend to leave more offspring than those less suited to the environment. This is natural selection. If the traits that confer greater reproductive success in the environment are heritable, the population will come to consist of more and individuals with those traits.
  

II. Population genetics.

          A. Define population genetics

• Distinguish between population genetics and Quantitative genetics
• Explain the meaning if the phrase: neo-Darwinian Synthesis

B. Define the following basic concepts related to population genetics.

• Mendelian Population = Deme
• Gene pool
• Allele frequency, polymorphism

C. Be able to calculate allele frequencies from genotypic frequencies, when the genotypic frequecies are known.

III Hardy Weinberg Law.

A. Explain why the Hardy Weinberg law was developed.

B. State the assumptions of the Hardy Weinberg Law. Note these assumptions are idealizations!

• Effectively infinitely large population
• Random mating
• No mutation
• No migration in or out of the population
• No natural selection

C. Be able to mathematically state and derive the Hardy Weinberg Law of Equilibrium:

Note: the Mathematical form of the law. p² + 2pq + q² = 1 where p and q are the allele frequencies for a particular gene locus.

• Expansion of binomial (p + q)² = 1.
  
• Can be expanded to situations where there are more than two alleles at a locus.
• Provides relationships between allele frequencies and genotypic frequencies
• Do the puzzler: Hardy Weinberg and multiple alleles

D. Explain the uses of the Hardy Weinberg law.

• Explain why dominant alleles do not increase in frequency if Hardy Weinberg assumptions are met.
• Calculate the frequency of recessive alleles given the frequency of homozygous recessive individuals in the population.

E. Explain the importance of Hardy Weinberg in population genetics

• Deviations from Hardy Weinberg equilibrium suggests evolution is at work-note that the opposite is not true!
  
• Most importantly allows us to systematically construct mathematical models to understand how evolution operates.

IV. Genetic variation

A. Explain why we are concerned about genetic variation in studying population genetics and evolution.

• Define genetic polymorphism.
• Define cline and explain how clines might arise.
• Explain the significance of the prairie vole example.
  

B. Identify the main ways scientists identify genetic variation today.

• At protein level using electrophoresis
• Polymorphic loci
• Heterozygosity(H)
• Classical vs neutral mutation model
• At the DNA level
• Restriction Fragment length polymorphisms (RFLPs).
  
• Single nucleotide polymorphisms - Protein electrophoresis misses many neutral and silent mutations.
• DNA length polymorphisms - involving  insertions/deletions within genes
• Short tandem repeats (STR's)
  

C. Distinguish between the classical and neutral models for polymorphism..

V. List and discuss the main agents of biological evolution as understood today

A. Mutation

• Source of genetic variation
• Protein synthesis and point mutation review.
• Mutations may be harmful or beneficial or neutral depending on the environment
• Mutation frequencies
  
• Equilibrium frequency
  

B. Genetic drift

• Explain how allele frequencies can change in the absence of natural selection in terms of sampling variance.
  
• Define effective population size(Ne)
  
• Define the concepts of founder effect and the bottleneck effect.
  
• Explain why genetic drift is an important consideration in wildlife conservation.
• Use standard formulas related to genetic drift.
  

C. Natural selection.

• Explain the distinction between natural and artificial selection
• Define Darwinian fitness.
• Distinguish between constant fitness models vs frequency dependent selection.
  
• Compute fitness values and selection coefficients for simple two allele models.
  
• Show the general procedure for determining change in allele frequency caused by natural selection.
  
• Apply formulas for change in allele frequencies for special cases summarized in your text.
  
• Review the online activity: Hardy Weinberg and Natural Selection.
• Conduct graphical stability analysis of simple selection models.
  

D. Explain the importance of migration as an agent of evolution

E. Distinguish between the different types of Non random mating

• Assortative (Positive and negative)
• Inbreeding. Incest, consanguineous matings.
• Sexual selection.
  

VI. Discuss the mechanisms by which we believe speciation happens. 

A. Distinguish between allopatric versus sympatric speciation (not in text)

B. Distinguish between the main types of barriers to gene flow and give examples:

D. List the main types of prezygotic isolation (Temporal, Ecological, Behavioral) and give examples.

Note: Prezygotic mechanisms often evolve as adaptations favored by evolution since individuals who avoid mistakes in mating have higher Darwinian fitness

pgd 11/01/02 revise 11/24/03