Population Genetics

Question 1

Population genetics

Answer 1

quantitative study of the distribution of genetic variation in populations and how the frequencies of genes and genotypes are maintained or changed

Question 2

Hardy-Weinberg principle

Answer 2

• applied to populations to estimate genotype frequencies in the population when allele frequency is known.
• If p is the frequency of allele A and q is the frequency of allele a in a gene pool:
• –The chance of an AA genotype is p2
• –The chance of an aa genotype is q2
• –Then chance of an Aa genotype is 2pq

Question 3

Hardy-Weinberg equation

Answer 3

(p+q)2 = p2 + 2pq + q2

Question 4

The Hardy-Weinberg is used to determine

Answer 4

the frequency of genotypes based on expressed phenotypes for autosomal recessive diseases

Question 5

Phenotypes of homozygotes for recessive mutant alleles can be identified and their frequency is equal to _______ in the Hardy-Weinberg eqn

Answer 5

q2

Question 6

Taking the square root of _______ and subtracting it from 1 yields _______

Answer 6

q2
p (the number of wild-type alleles in the population)

Question 7

Plugging p and q back into the equation gives the frequencies of the _______ and_______ genotypes (genotypes that we would not be distinguishable based on phenotype alone)

Answer 7

AA

Aa

Question 8

In order for the Hardy Weinberg principle to be upheld, a number of assumptions are made (4)

Answer 8

1. The population is large and mating is random
2. Allele frequencies remain constant over time (meaning no new mutations)
3. All individuals are equally capable of mating and passing on their genes (certain alleles are not selected for)
4. There has been no significant immigration of individuals with significantly different allele frequencies

Question 9

_______ is the main determinant in whether or not a mutant gene is passed onto future generations in order to become stable in a population

Answer 9

Fitness

Question 10

Fitness

Answer 10

describes the number of offspring of persons affected by a mutation survive to reproductive age

Question 11

For an autosomal dominant disease: µ =

Answer 11

0.5 F (1-f)

Question 12

For an autosomal recessive disease: µ =

Answer 12

F(1-f)

Question 13

For an X-linked recessive disease: µ =

Answer 13

0.333 F (1-f)

Question 14

A mutant allele that is as likely to represented in the next generation as the wild-type allele has a fitness of

Answer 14

1 (f=1)

Question 15

a mutant allele that causes death or sterility has a fitness of

Answer 15

0 (f=0)

Question 16

Autosomal recessive mutations

Answer 16

generally have little short-term effect on allele frequencies in populations. The number of expressed mutations is generally much lower than the frequency of heterozygotes. Most of the recessive alleles are hidden in heterozygotes and are unaffected by selection.

Question 17

_______ and _______ occur at approximately the same rate as recessive mutations, but perturb the allele frequency of a population to a greater extent because they are expressed to a greater degree and are, therefore, selected for at a higher frequency.

Answer 17

X-linked

autosomal dominant mutations

Question 18

The effect of a mutation in a population is amplified when _______ exists.

Answer 18

consanguinity

Question 19

Consanguinity

Answer 19

increases the frequency of mating between carriers of an autosomal recessive disorder.
This allows for a higher frequency of offspring homozygous for the recessive mutant allele.
As a result, rare recessive disorders are more frequent in these populations

Question 20

Other factors that cause the frequency of mutated alleles to shift from what would be predicted by the Hardy-Weinberg principle are

Answer 20

population stratification, assortative mating, genetic drift and migration

Question 21

How do physicians contribute to the increase in prevalence of genetic illnesses?

Answer 21

decreasing selection against mutant genes that would otherwise have a deleterious effect.

• inc the fitness of mutant alleles by improving their health & reproductive capacity
• mutant alleles able to make it to reproductive age and pass on their mutant alleles onto future generations