Lecture 5

Question 1

Fisher, Haldane and Wright’s Neo - Darwinism

Answer 1

Continuous variation and Darwinian natural selection are completely consistent with Mendel’s Laws, demonstrating evolutionary significance of genetic diversity

Question 2

3 Key Questions in Ecological and Evolutionary Genetics

Answer 2

1. What forces influence GD patterns in populations?
2. How can one measure the amount of GV in populations?
3. How much and what types of genetic variation occur in populations?

Question 3

5 Forces that Influence Patterns of Genetic Diversity and Evolution

Answer 3

1. Mutation
2. Recombination
3. Genetic drift
4. Gene flow
5. Natural selection

Question 4

Gene flow vs. genetic drift

Answer 4

Gene flow: movement of new alleles into an existing gene pool through immigration

Genetoc drift: random events that result in a different allele frequency: significant decrease or increase of a population size that result in more organisms with a particular trait surviving

Question 5

How the 5 Processes Influence Genetic Diversity

Answer 5

Mutation, recombination and gene flow increase diversity
Genetic drift decrease diversity
Natural selection can do both

Question 6

Metrics of Genetic Variation

Answer 6

Heterozygosity and polymorphism

Question 7

Definition of Heterozygosity

Answer 7

Fraction of individuals that are heterozygous, average across gene loci

Question 8

Definition of Polymorphism

Answer 8

Proportion of gene loci that have 2 or more alleles in the population; possible without heterozygosity

Question 9

2 Modes of the Maintenance of Genetic Variation

Answer 9

1. Mutation selection balance: less fit types reintroduced by mutation, followed by selection acting to remove them
2. Selection maintaining variation: heterozygote advantage, frequency - dependent selection. Fitness varies in space or time

Question 10

2 schools of thought on how much genetic variation occurs in natural populations

Answer 10

Morgan, Muller: classical: low heterozygosity and polymorphism, wild type is normal genotype, selection typically negative

Dobzhansky, Ford: balance: heterozygote advantage, high heterozygosity and polymorphism, selection favours diversity

Question 11

Cytology Definition

Answer 11

Study of cells

Question 12

What do evolutionary responses of continuous traits demonstrate?

Answer 12

Existence of heritable variation in fitness - related phenotypes

Question 13

Responses to artificial selection demonstrate…

Answer 13

Abundant genetic variation exiss for polygenic quantitative traits

Question 14

Allozyme gel electrophoresis

Answer 14

Different allelic forms of the same protein that undergo gel electrophoresis

Question 15

Application of allozyme gel electrophoresis

Answer 15

Determinign the proportion of genes that are variable and measures the diversity of genes that encode enzymes and proteins

Question 16

Monomorphic vs polymorphic genes on the gel electrophoresis

Answer 16

Monomorphic: single line
Polymorphic: more than one line with different spots on different coordinates

Question 17

Advantages of Studies of Enzyme Polymorphism

Answer 17

1. Many loci examined
2. Used in nearly any organism
3. Loci codominant, heterozygotes can be determined
4. Variation examined close to DNA level
5. Provides genetic marker loci for other studies

Question 18

Selectively Neutral Variation

Answer 18

Different types do not differ in their fitness relative to each other; new mutations neither eliminated nor retained by selection

Question 19

First Allozyme Studies

Answer 19

1. Mutation seelction balance: less fit types maintained
2. Selection maintaining variation: heterozygote advantage, frequency dependent selection
3. Selectively neutral variation

Question 20

The Kimura Neutral Theory

Answer 20

Most molecular variation may be selectively neutral
- Positive selection fixes beneficial mutations while negative selection eliminates detrimental mutations
Only ones left are neutral

Question 21

Genetic Variation at the DNA Level

Answer 21

Direct inference of genetic differences, genetic code for genes can distinguish changes that alter protein from those that don’t