Population Genetics

Question 1

What is population genetics?

Answer 1

The study of the distribution of genetic variation in a population.

Question 2

gene pool

Answer 2

collection of all the alleles at a particular locus in a population

Question 3

Key assumptions for Hardy-Weinburg equilibrium

Answer 3

1. No new mutations
2. No evolutionary selection
3. No migration
4. Infinitely large population
5. Matings are random

Question 4

How to calculate the carrier frequency

Answer 4

Calculate 2pq

Question 5

Problems with random mating

Answer 5

1. Stratification
2. Assortative mating
3. Consanguinity

Question 6

Maple Syrup Urine Disease

Answer 6

• consanguinity
• caused by founder effect: original founder carried allele
• genetic isolates

Question 7

What is evolution?

Answer 7

The process whereby the fittest alleles are selected

Question 8

Fitness (f)

Answer 8

A measure of the number of offspring of affected persons who survive to reproductive age

Question 9

f=0

Answer 9

• causes death

- no fitness

Question 10

f between 0 and 1

Answer 10

-deleterious

Question 11

f=1

Answer 11

just as likely to be represented in next generation as wild type allele

Question 12

Coefficient of selection

Answer 12

• the proportion of mutant alleles that are not passed on and are lost because of selection
• s = 1 - f

Question 13

If s = 1, it means….

Answer 13

it is a genetic lethal

Question 14

Why is selection on autosomal recessive disorders slow/ineffective?

Answer 14

• Most individuals with recessive allele are heterozygous
• Heterozygotes have the same phenotype (and fitness) as homozygous dominant individuals
• Selection can only act on expressed traits.

Question 15

Why does selection on autosomal dominant disorders happen much more quickly?

Answer 15

• Exposed to selection
• Heterozygotes have the same phenotype as homozygous dominant individuals, so they will also be selected against
• If zero fitness, new cases have to come from de novo mutation

Question 16

Genetic drift

Answer 16

changes to allele frequencies due to random chance/sampling error

Question 17

Population bottlenecks

Answer 17

Occur when many member of a group die, and few remain to re-start the population

Question 18

Fixed allele

Answer 18

the only allele for a single gene in the population

Question 19

Lost allele

Answer 19

No longer found in the population

Question 20

Loss of heterozygosity

Answer 20

As we get drift towards loss/fixation, heterozygote frequency decreases

Question 21

Does heterozygosity increase or decrease with every generation with a fixed population?

Answer 21

decrease

Question 22

Characteristics of an ideal population

Answer 22

1. males = females
2. All animals can reproduce
3. All animals equally likely to produce offspring
4. Mating is random
5. Population size is constant
6. No migration/mutation/selection

Question 23

Effective population size equation

Answer 23

Ne = 4(Nm)(Nf)/(Nm + Nf)