Lec: 17- Models and measurements

Question 1

What factors influence patterns of genetic diversity and evolution?

Answer 1

1) mutations
2) Recombination
3) Genetic Drift
4) Natural Selection:
a) Purifying (negative) selection: Removes genetic variation

b) positive (directional) selection: mutations that increase fitness get fixed, it also reduces genetic variation

c) selection from diversity: Natural selection can maintain the diversity over long term

5) Migration (gene flow): increase in genetic diversityin populaiton, migration influences the structuring of density over large scale.

Question 2

How can you measure genetic variation?

Answer 2

Using heterozygosity, fraction of individuals that are heterozygous averaged across gene loci.

Using polymorphism: Propotion of gene loci that have 2 or more alleles in the population

(a locus can be polymorphic) without being heterozygoes

Question 3

What maintains genetic variation?

Answer 3

1. MUTATION-SELECTION BALANCE: less fit types are reintroduced by mutations, followed by selection removing them
2. Selection maintaining variation: Heterozygous advantage

Frequency dependent selection

fitness varies over space and time , Aka BALANCE SELECTION

Question 4

What are the two types of school?

Answer 4

Classical: Morgan, muller emphasied the idea of negative selection

Thought there is less hyterozygous, low polymorphism

Wild type is normal genotype

Balance: Ford, Debronsky emphasized the idea of Heterozyygote advantage

Thought there is high hyterozygous, high polymorphism

Selection favours diversity

Question 5

What did first allozymic studies show in humans?

Answer 5

High genetic variation

Question 6

WHAT did the neutral theory suggest?

Answer 6

Negative selection rapidly eliminates detrimental mutations

Positive selection rapidly fixes beneficial mutations

The only mutations left to create genetic variation are selectively neutral