Population Genetics

Question 1

Four main evolutionary forces affect allele frequencies:

Answer 1

natural selection, genetic drift, mutation and

gene flow

Question 2

Mutation:

Answer 2

any change in the nucleotide sequence and/or arrangement of DNA (as compared to some reference standard).

Question 3

Polymorphism:

Answer 3

A genetic variant (mutation) which is common (>1%) in the populations

Question 4

Founder effects:

Answer 4

a high frequency of a mutant allele in a population founded by a small ancestral group when one or more of the original founders was a carrier of the mutant allele (Ghengis khan?)

Question 5

Genetic drift:

Answer 5

random fluctuation of allele frequencies, usually in small populations

Question 6

Selection:

Answer 6

active selection of favorable alleles over non-favorable ones

Question 7

fitness:

Answer 7

a measure of the chance an allele will be transmitted to the 
next generation (Scale is 0-1). Fitness measures reproductive success.

Question 8

Idealized Assumptions in Hardy-Weinberg Equilibrium (HWE):

Answer 8

Large population mating randomly.
• Allele frequencies remain constant over time because:
o No appreciable rate of new mutation
o No selection for/against any allele
o No appreciable immigration/emigration of persons from population with different allele frequencies

Question 9

Stratification

Answer 9

refers to populations containing 2 or more subgroups which tend preferentially mate within their own subgroup. Mate selection is not dependent on the trait/disease or
interest. (Example: sickle cell anemia in African Americans (AAs) has higher incidence social stratification favoring mating of AAs with other AAs, than is predicted by HWE)

Question 10

Assortive mating

Answer 10

refers to when the choice of mate is dependent (in part) on a particular trait (or sometimes a disease). This occurs because people tend to choose mates who resemble 
themselves for (language, intelligence, height, skin color, etc.). This has been observed for congenital short stature (previously called ‘dwarfism’), blindness, and deafness

Question 11

Two equations of Hardy-Weinberg?

Answer 11

p2 + 2pq + q2 = 1 and p + q = 1

Question 12

p =

Answer 12

frequency of the dominant allele in the population

Question 13

q =

Answer 13

frequency of the recessive allele in the population

Question 14

p^2 =

Answer 14

percentage of homozygous dominant individuals

Question 15

q^2 =

Answer 15

percentage of homozygous recessive individuals

Question 16

2pq =

Answer 16

percentage of heterozygous individuals