Lecture 26

Question 1

Define population genetics

Answer 1

Study of the distribution and change in frequency of alleles within populations

Question 2

Define evolution

Answer 2

Change in gene frequency over time in a population - which leads to speciation and divergence

Question 3

Define natural selection

Answer 3

Differential survival and reproduction of individuals due to differences in phenotype

Question 4

Define artificial selection

Answer 4

Intentional reproduction of individuals in a population with desirable traits

Question 5

Define homozygous by “descent” and “state”

Answer 5

Descent: alleles descended from the same copy in a common ancestor

State: alleles that are the same in structure and function but are descended from two different copies in ancestors

Question 6

What is a heterozygote advantage (overdominance) and heterozygote disadvantage (underdominance)?

Answer 6

Overdominance: heterozygotes favored over homozygotes and have a reproductive advantage which maintains both alleles in the population

Underdominance: heterozygote has a lower fitness than both homozygotes; leads to unstable equilibrium

Question 7

Explain how an isolated population can be useful for identifying rare genetic variation

Answer 7

Isolated populations tend to have more inbreeding, which leads to less variation among organisms in this population; when a rare genetic variation shows up, it is easily identifiable because all of the organisms are very similar, so the variation will stick out

Couldn’t find this in the lecture, so this is just the best answer I could come up with for this question

Question 8

Define population

Answer 8

Group of interbreeding, sexually reproducing individuals sharing a common set of genes

Question 9

What are some evolutionary forces that can affect gene frequencies and lead to genetic variation?

Answer 9

Mutation, gene flow, genetic drift, nonrandom mating, and natural selection

Question 10

What is the Hardy-Weinberg Law and what assumptions does it make?

Answer 10

Law: allele and genotype frequencies in a population will remain constant from generation to generation in the absence of other evolutionary influences (1908)

Assumptions: population is large, randomly mating and not affected by mutation, migration, or natural selection

Question 11

What is the Hardy-Weinberg equation?

Answer 11

p^2 + 2pq + q^2 = 1

p^2 = homozygous dominant allele pair frequency
q^2 = homozygous recessive allele pair frequency
2pq = heterozygous allele frequency

Question 12

Define positive and negative assortive mating

Answer 12

Positive: tendency of like individuals to mate

Negative: tendency of unlike individuals to mate

Question 13

Define interbreeding

Answer 13

Measure of the probability that 2 alleles are identical by descent; inbreeding increases the percentage of homozygous individuals in the population

Question 14

What is inbreeding depression?

Answer 14

Increased appearance of lethal and deleterious traits with inbreeding

Question 15

Define outcrossing

Answer 15

Avoidance of mating between related individuals

Question 16

What are some positives that come from inbreeding?

Answer 16

Uncovers deleterious alleles and can lead to the elimination of these alleles in the population; also keeps together good combinations of genes that might be broken up by outcrossing

Question 17

Define nonrandom mating (sexual selection)

Answer 17

Occurs when the probability that 2 individuals in a population will mate is not the same for all possible pairs of individuals

Question 18

Define migration

Answer 18

Movement of populations, groups, or individuals; in genetic terms, migration enables gene flow (the movement of genes from one population into another)

Question 19

Define genetic drift

Answer 19

Change in the frequency of a gene variant (allele) in a population due to random sampling of organisms

Question 20

What are causes of genetic drift? Define them

Answer 20

Founder effect: reduced genetic diversity that results when a population is descended from a small number of colonizing ancestors

Genetic bottleneck: sharp reduction in the size of a population due to environmental events (earthquakes, floods, fires, disease, or droughts) or human activities (genocide)

Question 21

Define directional selection

Answer 21

Type of selection in which one allele or trait is favored over another

Question 22

What is the expected frequency of heterozygotes in a population with allelic frequency X and Y that is in Hardy-Weinberg? (.5 each)

Answer 22

2XY: 2 x 0.5 x 0.5 = 0.5 = 50%

Question 23

What is the effect of outcrossing on a population?

Answer 23

Allelic frequency changes