LECTURE 16 (Pop gen 1)

Question 1

who are the three fathers of pop genetics and what did they do?

Answer 1

• fisher: sexual selection theory
• Haldane: concept of fitness
• Wright: concept of genetic drift

Question 2

What’s evolution?

Answer 2

change iin allele frequency through generations

Question 3

what’s a population?

Answer 3

a group of interbreeding individuals, there’s discrete or overlapping populations.

Question 4

what do we need to study genetic variation in a population

Answer 4

biological markers

Question 5

Whats genetic variation?

Answer 5

number of alleles at a loci and their frequency

Question 6

what are allozymes?

Answer 6

they’re variant form of enzymes that have different alleles at the same locus, can serve as molecular markers, they’re neutral and co-dominant
when in a gel they can make easy to distinguish homo from hetero.

Question 7

what does it mean that a marker is neutral?

Answer 7

reflect genetic variation in a pop

Question 8

what does it mean that a marker is codominant?

Answer 8

that let distinguish bt homo and hetero

Question 9

What’s a pop in H-W eq?

Answer 9

a population whose allele freq does not change through time bc there’s no migration, mutation or selection .

Question 10

characteristics of HW.

Answer 10

• no migration
• no seleciton
• no mutation
• no drift
• random mating
• large pop
• no overlapping pop (discrete pop)
• equal sex ratio

Question 11

when an allele is rare it occurs at the homo or hetero form?

Answer 11

mainly at the hetero form

Question 12

what are the 5 steps to calculate whether a pop is in HW eq?

Answer 12

1. observed number: you need to calculate the number of A alleles, a alleles and total number of alleles A= 2AA+ Aa a= 2aa+Aa tot number = 2AA + 2aa + 2 Aa
2. calculate the allele frequencies: A= 2AA+ Aa/ tot =p
   a= 2aa+ Aa/ tot = q
3. expected genotype freq: calculate the genotype freq p^2 q^2 and 2pq
4. expected number of each genotype= multiply genotype frequency by the tot number of INDV
5. chi sq sum (O-E)^2// E

Question 13

how do we reject the null hyp?

Answer 13

when X value exceeds the critical value for the correct number of DF

Question 14

what’s the null hypothesis?

Answer 14

two populations are in HW eq, the reject of the null hip means that one of the assumptions of HW eq are not met

Question 15

what are the limitations of HW eq?

Answer 15

1. pop are not infinitely large (drift occurs)
2. further analysis is required (replication)
3. bewared when looking a sub pop bc they might be in walhund effect
4. x^2 is sensitive to small populations and small deviations from HW might not be picked up

Question 16

what can cause a deficit in heterozygotes?

Answer 16

walhund effect or methodological issues