Genetic drift and Gene flow

Question 1

What are two examples of extreme genetic drift?

Answer 1

Bottleneck effect and Founder effect

Question 2

Bottleneck effect

Answer 2

acceleration of genetic drift that occurs when a population’s size is significantly reduced for one generation or more; overhunting and natural disasters can cause this; Ex: cheetahs have experienced population declines due to human encroachment and as a result have extremely low genetic diversity

Question 3

Founder effect

Answer 3

acceleration of genetic drift that occurs when a small number of individuals become isolated from a larger population; Ex: island populations of Pacific wrens have much lower genetic diversity vs. the mainland

Question 4

In a population at HWE w/ alleles A (p = 0.1) and a (q = 0.9), what is the frequency of aa?

Answer 4

q^2 = 0.9^2 = 0.81

Question 5

If we did the marble sampling example again, would we get the same result (of the blue (A) allele frequency continuously increasing)?

Answer 5

No it’s random

Question 5

Buri drift experiment

Answer 5

The experiment tracked eye color in flies across multiple generations of random sampling in multiple populations. The various eye traits were red homozygous, heterozygous (orange), and white homozygous. The eye color is neutral in the lab, so any allele frequency changes were due to drift only.

Result: either red or white allele was fixed in most populations after 19 generations

Question 6

Fixation

Answer 6

when the allele frequency of one allele reaches 100%, also occurs more rapidly in small populations

Question 7

Dr. Buri observed evolution in populations of 16 flies for 19 generations in his drift experiment. Which of the following would we expect if he used populations of 1,600 flies for the same number of generations?

Only the red allele would be fixed

Drift would be weaker and fewer populations would have fixed one of the two alleles

Drift would be stronger and more of the populations would have fixed one of the two alleles

Only the white allele would be fixed

Answer 7

Drift would be weaker and fewer populations would have fixed of the two alleles (due to the fly population becoming larger)

Question 8

Gene flow

Answer 8

movement of alleles between populations due to migration; tends to make populations more genetically similar over time

Question 9

Migration

Answer 9

movement of an individual from one population to another

Question 10

Maladaptive

Answer 10

when alleles from a diff. environment are introduced to a new environment they might not be favored

Question 10

Genetic swamping

Answer 10

the reduction in a population’s ability to adapt due to gene flow from a maladapted population

Question 11

Adaptive introgression

Answer 11

the movement of beneficial (adaptive) alleles between populations, which facilitates adaptations

Question 12

Differences between genetic drift and gene flow.

Answer 12

Genetic drift:
-Allele frequencies change due to chance
-Small populations are more affected by genetic drift
-Founder effect and bottlenecks accelerate genetic drift

Gene flow:
-Allele frequencies change due to migration
-Gene flow causes allele frequencies to be similar in time
-Gene flow/Migration can introduce new alleles in a population

Question 13

The conversion of quality habitat into farmlands has greatly depleted the greater prairie chicken populations, and as a result, their genetic diversity. Which of the following occurred in this example?

Founder effect

Gene flow

Natural selection

Bottleneck effect

Answer 13

Bottleneck effect