5-2-2 Mutation Rate

Question 1

Mutation rate of a given gene vs. mutation rate within a population

Answer 1

The DNA replication and repair process keep the mutation rate of a given gene low.

The mutation rate within a population is higher than the mutation rate of a single gene, because each individual has many genes and a population has many individuals.

Question 2

Does mutation rate differ among different species?

Answer 2

Yes, mutation rate varies greatly among species and even among the genes of an individual.

Question 3

What is gene flow?

Answer 3

Movement of alleles in or out of a population due to migration of breeding animals.

The flow of alleles increases the population’s gene pool.

Continued gene flow between populations will decrease differences between the populations.

Restricting gene flow between populations may give rise to new species.

Question 4

Random mating vs. non-random mating

• Random mating
• Non-random mating:
  
  • Inbreeding
  • Assortative mating

Answer 4

Random mating: Individuals pair by chance.

Inbreeding: mating between relatives. (This does not change allele frequency, but it decreases the relative number of heterozygotes.)

Assortative mating: Individuals mate with those that have the same phenotype. (This divides a population into two phenotypic classes.)

Question 5

What is genetic drift?

(Also called the “founder effect”)

Answer 5

Genetic drift (also known as the “founder effect”) can happen when a small population with reduced gene pool is created in which chance (rather than natural selection) can cause the allele frequency to change.

Example: The Pilgrims founded a colony (a small isolated population) with a reduced gene pool, in which rare alleles could occur at higher frequency than in the general population, and alleles present in the general population might not be present in the isolated population.

Question 6

Examples of “genetic drift”, or “founder effect”

Answer 6

1. Many island species (such as Darwin’s finches on the Galapagos islands) display founder effects in which an island species varied from the mainland species and from species on other islands.
2. The Pilgrims founded a colony (a small isolated population) with a reduced gene pool, in which rare alleles could occur at higher frequency than in the general population, and alleles present in the general population might not be present in the isolated population.

Question 7

Bottleneck - a type of genetic drift

Answer 7

Natural disasters or predation can cause a drastic short-term drop in the size of a population. The survivors may represent only a small portion of the orignal gene pool. Even when the population returns to its original size, a portion of the original genetic diversity remains lost.

This phenomenon is called a “bottleneck”. It is a type of genetic drift.