Unit 5 - Ch 19 - Population Genetics

Question 1

Population

Answer 1

All members of a single species in one location and time.

Question 2

Gene pool

Answer 2

sum total of all alleles in a population for a single genetic trait.

Question 3

Gene Frequency

Answer 3

Proportion of dominant and recessive alleles in a gene pool. Expressed decimally

Question 4

Hardy Weinberg Equilibrium predicts that:

Answer 4

Gene frequencies in a population remain constant under ideal conditions (assumptions)

Question 5

Equation for Hardy Weinberg Equilibrium

Answer 5

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

p = frequency of dominant allele
q = frequency of recessive allele

Question 6

What is p2

Answer 6

proportion of the population expected to be homozygous dominant

Question 7

What is 2pq

Answer 7

proportion of the population expected to be heterozygous

Question 8

What is q2

Answer 8

proportion of the population expected to be homozygous recessive

Question 9

What is p2 + 2pq

Answer 9

proportion of dominant phenotypes

Question 10

Assumptions of Hardy Weinberg Equilibrium - (5) these are assumed to be true

Answer 10

1. Random Mating - no mate selection between different phenotypes
2. No Mutations - mutations change gene frequency. This can be met over the short term.
3. No Net Migration - immigrants or emigrants representative of the entire population
4. Large Population - minimizes the impact of chance events on the population
5. No Selective Advantage - both phenotypes are equally successful in the environment

Question 11

In a population of 100 people, we find 49 that have the recessive phenotype for an autosomal trait. Frequency of recessive allele?

Answer 11

q = .7

Question 12

In a population, 16% of the women are colorblind (XbXb). What % of men would be expected to be colorblind?

Answer 12

q = 40%

Question 13

If 20% of the men are colorblind in a population, how many women would you expect to be carriers of the colorblind trait?

Answer 13

2pq = xBxb = 32%

Question 14

Factors Which Alter Gene Frequency (4)

Answer 14

Mutation
Net migration
Genetic drift
Selection

Question 15

Mutations in a population

Answer 15

Usually a small impact in populations

1. A to a = 1/10,000
   changing a coding allele to a non-coding allele
2. a to A = 1/10,000,000
   non-coding allele to coding allele

Question 16

Net migration in a population

Answer 16

Immigrants or emigrants with different gene frequencies than the original population. Results in gene flow between populations (tends to blend them)

Question 17

Genetic drift in a population and 2 examples

Answer 17

Change in gene frequency due to chance. This is more likely to occur when population is small.

1. Founder Effect - small group forms (founds) a new population.
   Amish => high frequency of polydactylism and genetic form of dwarfism
2. Population Bottleneck - occurs when a population is drastically reduced in numbers and survivors rebuild the population.

Question 18

Selection in a population

Answer 18

Allowing only certain individuals to breed

1. Artificial - humans determine who breeds
2. Natural - nature determines who reproduces