Variation at the Population Level

Question 1

What is the central issue in population genetics?

Answer 1

Genetic variation

Question 2

What are the 3 questions about genetic variation in population genetics?

Answer 2

1. What is the extent within populations
2. Why is it there
3. How does it change over many generations

Question 3

What is the gene pool?

Answer 3

All alleles of every gene in a population

Question 4

What do population geneticists study?

Answer 4

Genetic variation within the gene pool and how it changes from one generation to the next

Question 5

What is a phenotype?

Answer 5

Characteristic of an individual organism

Question 6

What is a genotype?

Answer 6

Genetic constitution of an individual

Question 7

What is a locus?

Answer 7

Place on a chromosome, gene that occupies a site

Question 8

What is an allele?

Answer 8

A particular form of a gene, distinguishable by its effects on phenotype

Question 9

What is a haplotype?

Answer 9

A set of alleles that is a DNA segment that can be distinguished from homologous sequences

Question 10

What is a gene copy?

Answer 10

Number of representatives of a gene. Ex. 200 gene copies with 100 2N individuals

Question 11

What is an allele frequency?

Answer 11

Relative proportion of a particular allele at a particular locus in a population, the relative commonness or rarity of an allele

Question 12

What is a genotype frequency?

Answer 12

Relative proportion of a particular genotype in a population

Question 13

What is a population?

Answer 13

A group of individuals of the same species living in the same region at the same time

Question 14

What is a deme?

Answer 14

A smaller local population that is part of a larger population

Question 15

Why do demes have different gene pools than other demes within a larger population?

Answer 15

They are often isolated by moderate geographic barriers and are more likely to interbreed with each other

Question 16

How do you calculate the total number of alleles in a diploid population?

Answer 16

Number of individuals x 2

Question 17

How do you calculate the total number of a certain allele in a population?

Answer 17

Add two copies for each homozygote and one copy for each heterozygote

Question 18

How do you calculate the allele frequency in a population?

Answer 18

Number of copies of an allele in a population/ total number of gene copies in a population

Question 19

How do you calculate the genotype frequency in a population?

Answer 19

Number of individuals with a particular genotype in a population/ total number of individuals in a population

Question 20

What should the total frequency of all alleles add up to?

Answer 20

1

Question 21

What is a monomorphic gene? What should the allele frequencies be?

Answer 21

A gene with only 1 allele. The frequency will be 1 or close to 1

Question 22

What is the Hardy-Weinberg equilibrium?

Answer 22

A simple mathematical expression that relates allele frequencies and genotype frequencies in a population

Question 23

Is the Hardy-Weinberg equilibrium a null or alternative hypothesis?

Answer 23

Null hypothesis. Predicts that allele and genotype frequencies will not change over the course of many generations

Question 24

What are the 5 assumptions of the Hardy-Weinberg equilibrium?

Answer 24

1. No mutations
2. No gene flow
3. Random mating
4. No natural selection
5. Extremely large population

Question 25

What does it mean if the assumptions of the Hardy-Weinberg equilibrium are met?

Answer 25

The population is not evolving

Question 26

Why does the Hardy-Weinberg equilibrium assume no mutations?

Answer 26

Mutations will modify the gene pool

Question 27

Why does the Hardy-Weinberg equilibrium assume random mating?

Answer 27

Individuals showing preference in breeding will change genotype frequencies

Question 28

Why does the Hardy-Weinberg equilibrium assume large populations?

Answer 28

Small populations are very prone to random genetic drift

Question 29

Why does the Hardy-Weinberg equilibrium assume no gene flow?

Answer 29

Immigration and emigration will change allele frequencies

Question 30

Why does the Hardy-Weinberg equilibrium assume no natural selection?

Answer 30

Natural selection will lead to certain alleles becoming more common and other alleles becoming less common

Question 31

What does it mean when any of the Hardy-Weinberg equilibrium assumptions are violated?

Answer 31

The population is evolving

Question 32

What is the Hardy-Weinberg equilibrium formula for a gene with 2 alleles?

Answer 32

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

Question 33

What is p^2 in the Hardy-Weinberg equilibrium formula?

Answer 33

The genotype frequency of homozygous dominant individuals in the population

Question 34

What is 2pq in the Hardy-Weinberg equilibrium formula?

Answer 34

The genotype frequency of heterozygous individuals in the population

Question 35

What is q^2 in the Hardy-Weinberg equilibrium formula?

Answer 35

The genotype frequency of homozygous recessive individuals

Question 36

Does the Hardy-Weinberg equilibrium describe a hypothetical or real population?

Answer 36

Hypothetical. In reality none of the assumptions would likely be met

Question 37

What is p in the Hardy-Weinberg equilibrium?

Answer 37

Allele frequency of dominant allele

Question 38

What is q in the Hardy-Weinberg equilibrium?

Answer 38

Allele frequency of the recessive allele

Question 39

How might a natural population be in Hardy-Weinberg equilibrium?

Answer 39

A population can be evolving at some genes and be in Hardy-Weinberg equilibrium at other genes

Question 40

How is the phenylketonuria locus in Hardy-Weinberg equilibrium?

Answer 40

It is an autosomal recessive disorder. There is low mutation rate, mate selection is random with respect to that gene, natural selection can only act on homozygous recessive individuals that don't follow the diet, population is large, and migration has no effect

Question 41

What does it mean when a population is at Hardy-Weinberg equilibrium?

Answer 41

Allele frequencies are not changing from generation to generation

Question 42

What are the steps to determine if a population is at Hardy-Weinberg equilibrium?

Answer 42

1. Calculate allele frequencies 2. Calculate the expected genotype frequencies (using p^2, 2pq, and q^2) 3. Multiply genotype frequencies by the population size to get the expected number of individuals 4. Compare the genotype frequencies in a population with the expected number of individuals 5. If expected number of individuals with that genotype is + or - 5% of the number of individuals with that genotype are the same, the population is at Hardy-Weinberg equilibrium

Question 43

What is sympatric population variation?

Answer 43

Variation among populations with overlapping geographic distributions

Question 44

What is parapatric population variation?

Answer 44

Variation among neighbouring populations that are adjacent, but don't overlap

Question 45

What is allopatric population variation?

Answer 45

Populations that are separated by geographic barriers

Question 46

What is a subspecies?

Answer 46

A recognizable distinct population occupying a different geographic area from others of the same species

Question 47

What is a cline?

Answer 47

Gradual change in a character or allele frequencies over geographic distance