Final: Population Genetics

Question 1

Calculating Genotypic frequencies

Answer 1

Number of individuals possessing the genotyp divided by the total number of individuals in sample.
f(AA)=#AA individuals/N
N: total # of individuals
f: freq each genotype

Question 2

Calculating Allelic Frequencies

Answer 2

Numbers of copies of a particular allele present in a sample divided by total number of alleles
Freq of allele=# copies of the alleles/# copies of all alleles at the locus in a population.

Question 3

Hardy-Weinberg Law
Assumption: (5)
Prediction 1:
Prediction 2:

Answer 3

Assumption: population is large, randomly mating, not affected by mutation, migration, or natural selection.
Prediction 1: The allelic frequencies of a population do not change.
Prediction 2: The genotypic Frequencies stabilize.

Question 4

p2:
q2:
2pq:

Answer 4

p2: homozygous dominant allele pair frequency
q2: homozygous recessive allele pair frequency
2pq: heterozygous allele frequency

Question 5

Population

Answer 5

a group of interbreeding, sexually reproducing individuals with a common set of genes.

Question 6

Genetic variation

Answer 6

variation in alleles - sequence variation / structural changes

caused by mutation
frequencies affected by evolutionary forces.

Question 7

Calculating frequency of a genotype:

Answer 7

number of individuals with the genotype/ total number of individuals.

Question 8

How does calculating allele frequencies for genes on the X chromosome differ from genes in the rest of the genome?

Answer 8

Since males only have one X chromosome they will only have 1 allele

Question 9

If the assumptions of H.W. are true, what does this confer about the next generation?

Answer 9

Genotypic frequencies are predictable for the next generation.

Question 10

Positive assortative mating:

Answer 10

a tendency of like individuals to mate

Question 11

Negative Assortative Mating:

Answer 11

A tendency of unlike individuals to mate

Question 12

Inbreeding

Answer 12

inbreeding is a measure of the probability that two alleles are identical by descent.

Question 13

Alleles identical by descent

Answer 13

alleles descended from the same copy in a common ancestor

Question 14

alleles identical by state

Answer 14

alleles that are the same in structure and function but are descendent from two different copies in ancestors.

Question 15

Inbreeding depression:

Answer 15

increased appearance of lethal and deleterious traits with inbreeding.
Inbreeding increases the percentage of homozygous individuals in the population.

Question 16

Outcrossing

Answer 16

the avoidance of mating between related individuals.

Question 17

What is the effect of outcrossing on a population?

Answer 17

there will be more heterozygotes than predicted by the H.W. law

Question 18

What doe forward and reverse mutations do to allele frequencies?

Answer 18

They can change allele frequencies, but eventually lead to a stable equilibrium if mutation rates remain constant.

Question 19

Genetic Drift

Answer 19

Changes in allele Frequency

Question 20

Causes of Genetic Drift

Answer 20

Founder Effect

Genetic Drift

Question 21

What are causes of genetic drift?

Answer 21

• Founders Effect

- Genetic Bottleneck

Question 22

Natural Selection: Define Fitness

Answer 22

Is the relative reproductive success of a genotype compared to other genotypes in the population.

• Fitness ranges from 0 to 1.
• to calculate fitness, take the average number of offspring produced by a genotype and divide it by the mean number of offspring produced by the most prolific genotype.

Question 23

Natural Selection: Selection Coefficient

Answer 23

Is the relative intensity of selection against a genotype.

-Selection coefficient equals 1- the fitness for a particular genotype.

Question 24

Natural Selection: Directional Selection

Answer 24

A type of selection in which one allele or trait is favored over another.

Question 25

Natural Selection: Overdominance (heterozygote advantage)

Answer 25

Both alleles are favored in the heterozygote and neither allele is eliminated from the population

Question 26

Natural Selection: Underdominance:

Answer 26

The heterozygote has a lower fitness than both homozygotes.

-This leads to an unstable equilibrium.

Question 27

What is the frequency of a recessive allele at equilibrium equal to?

Answer 27

It is equal to the square root of the mutation rate divided by the selection coefficient.

Question 28

What is the frequency of a dominant allele at equilibrium equal to?

Answer 28

it is equal to the mutation rate divided by the selection coefficient.

Question 29

Why is the recessive allele dependent on the square root of the mutation rate?

Answer 29

Because a recessive allele will be covered up by a dominant allele. Selection is a little slower. It will work on individuals that are heterozygous dominant.

Question 30

What are the short and long term effects of MUTATION?

Answer 30

Short: Change in allele frequency
Long: Equilibrium reached between forward and reverse mutations

Question 31

What are the short and long term effects of MIGRATION?

Answer 31

Short: Change in allelic Frequency
Long: Equilibrium reached when allelic frequencies of source and recipient population are equal

Question 32

What are the short and long term effects of GENETIC DRIFT?

Answer 32

Short: Change in allelic frequency
Long: Fixation of one allele

Question 33

What are the short and long term effects of NATURAL SELECTION?

Answer 33

Short: Change in allelic frequency
Long: Directional selection: fixation of one allele.
- Overdominant selection: Equilibrium Reached.