Migration, effective population size, & non-random mating

Question 1

What is migration?

Answer 1

the movement of individuals from one population to another, which results in the transfer of genes between those populations

Question 2

How does migration-selection balance maintain genetic variation within populations?

Answer 2

allowing the movement of new alleles from neighboring populations through migration

Question 3

If gene flow is the only evolutionary force acting on a set of populations, what is the ultimate impact on genetic variance among populations?

Answer 3

the entire population will be homogenic

Question 4

Can gene flow help maintain genetic variation within populations?

Answer 4

yes INCREASES genetic varience w/in populations

Question 5

T/F: migration functions the opposite of genetic drift

Answer 5

False
**migration IS genetic drift

Question 6

Define Effective Population Size.

Answer 6

the size of an idealized population in which the rate of genetic drift id the same as the actual population

Question 7

What 3 factors discussed in class lower the effective population size (Ne) relative to the census population size (N)?

Answer 7

-Ne= effective population size
-N = census
1. Variation in the number of progeny → example of elephant seals
* 6% of males get 88% of all matings
2. Unequal number of males and females → if a harem of elephant seals has 100 females under one male
* Ne = 41001 / (100+1) = 3.96
* The effective size of the harem is ~4% of the population size
3. Unequal numbers of males and females

Question 8

T/F: In population genetics equations, N typically refers to Ne.

Answer 8

False

Question 9

Understand Figure 7.17 in your text. Why did the heterozygosity decline faster than expected?

Answer 9

the population experienced a significant bottleneck event

Question 10

What is non-random mating? What is inbreeding?

Answer 10

Non-random mating is a situation where individuals in a population are not equally likely to mate with any other individual.
Inbreeding is the mating among genetic relatives in a form of nonrandom mating. This becomes a problem in small populations, and is a serious issue in conservation biology

Question 11

T/F: Inbreeding changes allele frequencies

Answer 11

false

Question 12

T/F: Inbreeding changes genotype frequencies

Answer 12

true

Question 13

What is the impact of inbreeding on the frequency of heterozygotes within a population? What is the impact of inbreeding on the frequency of homozygotes?

Answer 13

Inbreeding increases homozygosity

Question 14

Define the inbreeding coefficient, F? Understand how to use the equation

Answer 14

= the probability that two alleles are identical by decent
* both copies descended from the same ancestral allele in an earlier generation

Question 15

Compare and contast: autozygous, allozygous, homozygous, heterozygous. Is it possible to be homozygous and allozygous?

Answer 15

Autozygous → alleles that are IBD
Allozygous → the probability that 2 alleles are not IBD
Homozygous → alleles are the same
Heterozygous → alleles are different

Question 16

T/F: The probability of identity by descent = the inbreeding coefficient = the probability of autozygosity

Answer 16

True

Question 17

What is inbreeding depression? Why do we care about it?

Answer 17

-by increasing the frequency of homozygotes, inbreeding increases the probability of homozygous deleterious recessive alleles.
Ex) inbredding increses the incidence of Cystic Fibrosis in humans
-in wild populations inbreeding typically lowers the fitness of individuals and populations

Question 18

What are four ways by which animals or plants avoid inbreeding (as presented in class)?

Answer 18

-mate choice
-dispersal from natal site
-self-incompatibility loci in plants
-management move individuals between populations (aka gene flow) to combat the decline in heterozygosity