Hardy-Weinberg Equilibrium

Question 1

What are the assumptions of the HWE?

Answer 1

• mutations can be ignored
• migration is negligible (no gene flow)
• mating is random
• no selective pressure
• large population size
• equal allele frequencies in each sex

Question 2

What is the underlying principle of the HWE?

Answer 2

p + q = 1,

where p = dominant allele frequency
and q = recessive allele frequency

Question 3

What is gene flow and give an example?

Answer 3

• new alleles give rise to increased mutations
• new alleles introduced my migration/intermarriage
• new gene frequency

e.g. Vikings populating Ireland/Scotland

Question 4

Name two types of non-random mating?

Answer 4

Assortative mating; partners with shared characteristics

Consanguinity; mating between close blood relatives

Question 5

What happens as a result of negative natural selection?

Answer 5

• decreased fitness
• decreased trait prevalence
• decreased alleles

Question 6

What happens as a result of positive natural selection?

Answer 6

• increased fitness
• increased trait prevalence
• increased heterozygote advantage

Question 7

What is heterozygote advantage?

Answer 7

carrying the gene for a certain recessive condition can give rise to resistance on another condition

e.g. sickle cell anaemia = malaria resistance in tropical Africa
cystic fibrosis = cholera/typhoid resistance in western Europe

Question 8

What is genetic drift?

Answer 8

statistical drift of gene frequencies due to random events (beetles by the pond)

Question 9

What is the founder effect?

Answer 9

reduced variation when a small subset of a large population is used to start a new colony
(the bottleneck effect)