learning objectives 4

Question 1

Define evolution in genetic terms.

Answer 1

Evolution is the change in the gene pool over time.

Question 2

What is a gene?

Answer 2

A gene is a small region of a chromosome that codes for a molecule (usually a protein) which performs a function for a cell.

Question 3

Define allele frequency.

Answer 3

Allele frequency is the proportion of all the copies of a given gene that are a particular allele.

Question 4

How is allele frequency calculated?

Answer 4

Allele frequency = Number of a certain allele / Total number of alleles.

Question 5

What is the convention for allele frequencies?

Answer 5

Frequency of one allele = p; Frequency of the other allele = q; p + q = 1.

Question 6

Define population in genetic terms.

Answer 6

A population is a group of interbreeding individuals.

Question 7

What is genotype frequency?

Answer 7

Genotype frequency is the proportion of a specific genotype in a population.

Question 8

Define genotype count.

Answer 8

Genotype count is the number of individuals with a certain genotype.

Question 9

What is a gene pool?

Answer 9

A gene pool is the combination of all the genes (including alleles) present in a reproducing population or species.

Question 10

Why is there a shift in beetle colors through generations?

Answer 10

Due to natural selection, genetic drift, migration from other populations, or mutation.

Question 11

What is the purpose of testing for Hardy-Weinberg Equilibrium (HWE)?

Answer 11

To measure microevolution by comparing the expected genetic makeup of a population if it were not evolving to the observed population.

Question 12

What does it mean if observed genotype counts match expected counts under HWE?

Answer 12

The population is not measurably evolving, and mating is random.

Question 13

What does it mean if observed genotype counts differ from expected counts under HWE?

Answer 13

The population may be evolving, and the differences can provide clues about how.

Question 14

List the 5 conditions required for a gene in a population to be in HWE.

Answer 14

1. No genetic drift (large population)
2. No natural selection
3. No gene flow/migration
4. No new mutation
5. Random mating

Question 15

How do you calculate expected genotype frequencies under HWE?

Answer 15

For alleles p and q:

Frequency of homozygote TT = p²
Frequency of homozygote tt = q²
Frequency of heterozygote Tt = 2pq

Question 16

What statistical test is used to evaluate whether a population is in HWE?

Answer 16

A chi-squared (χ²) goodness of fit test.

Question 17

True/False: If p² + 2pq + q² = 1, the population is in HWE.

Answer 17

False, you must compare observed and expected genotype counts with a chi-squared test.

Question 18

What is genetic drift?

Answer 18

Genetic drift is the change in allele frequencies due to random sampling effects in finite populations.

Question 19

How does genetic drift affect allele frequencies?

Answer 19

It causes random changes, which are slower in medium/large populations but can reduce genetic variation over time.

Question 20

Describe the bottleneck effect.

Answer 20

A sudden change drastically and randomly reduces the population size, reducing genetic diversity and changing allele frequencies by chance.

Question 21

Describe the founder effect.

Answer 21

A small number of individuals start a new population, often with different allele frequencies from the source population due to chance.

Question 22

Does genetic drift occur in populations that remain the same size?

Answer 22

Yes, genetic drift occurs in every population, in every generation, but is stronger in small populations.

Question 23

How does natural selection affect allele frequencies?

Answer 23

It can select for some genotypes and against others, changing allele frequencies over time.

Question 24

What is gene flow, and how does it affect populations?

Answer 24

Gene flow is the transfer of alleles between populations, which can alter allele frequencies, reduce genetic differences among populations, and counteract the effects of natural selection.

Question 25

What is mutation’s role in evolution?

Answer 25

Mutation introduces new genetic variants and is essential for genetic variation, but its effects on allele frequencies are usually small over short time scales.

Question 26

Define assortative mating.

Answer 26

Assortative mating is non-random mating where individuals with similar genotypes are more likely to mate, often producing excess homozygotes.

Question 27

Define disassortative mating.

Answer 27

Disassortative mating is non-random mating where individuals with different genotypes are more likely to mate, often producing excess heterozygotes.