Lecture 34

Question 1

What is Hardy Weinberg equilibrium?

Answer 1

-genotypes are in the proportions if p= f(A) allele q = f(a) allele
p2+2pq+q2=1
p2= f(AA)
2pq=f(Aa)
q2=f(aa)
-remaining constant across generations
This equilibrium acts as a reference point for all population genetics studies
However constancy of allele frequencies does not necessarily
indicate a Hardy-Weinberg equilibrium
-when you have hardy weinberg equilibrium you can maintain the genotypic proportions from generation to generation

Question 2

What are the 5 assumptions of the Hardy-Weinberg law?

Answer 2

1. Random mating=equally likely to mate with everyone, no preference allowed
2. No migration (no gene flow)= no new alleles brought in
3. No selection acting= once a partner equally likely to have the same no. of offspring, none is more fit than the other
4. No mutation=no new alleles, or equally in both direction
5. Infinite population size = large enough to prevent sampling errors and random effects

Question 3

What does H-W refer to?

Answer 3

-genotypic frequencies remaining constant in the proportion and as a consequence constant allele frequencies result

Question 4

How do you know if population is in H-W equilibrium?

Answer 4

.

Question 5

What are selective agents?

Answer 5

-Factors in the environment which discriminate between phenotypes and or genotypes
eg.,
climate pollution predators disease insecticide antibiotics…….
Fitness can change in different environments

Question 6

What is w and s?

Answer 6

w-fitness and s is the selection against

• one phenotype always has fitness 1 and anotehr has less
• s = if w=0 then s=1

Question 7

what happens in a malarial region?

Answer 7

-in non malarial region HbA frequency tends towards monomorphism

malarial region = constant allele frequencies= stable or balanced polymorphism = but not HW because there is selection!
conclusion from sickle cell study: selection may alter allele frequencies or keep them constant

so sometimes even when have stable allele frequencies= doesn’t have to be HW equilibrium