Genetic variation - Lecutre 5

True Or False: Continuous variation and Darwinian natural selection are NOT consistent with Mendel’s law

False, they are

True Or False: Mutation is the ULTIMATE source of genetic variation

True

True Or False: Mutations are the ONLY source of genetic variation

False, there are others EX. recombination

Genetic drift, and it’s affects

Random change in frequency of alleles

• DECREASES genetic variation

3 types of natural selection

1. Negative selection / purifying selection

2. Positive selection / directional adaptation

3. Selection favoring diversity

Negative selection

• Negative mutations are removed

• DECREASES genetic variation

Positive Selection

• Positive mutations become fixed

• DECREASES genetic variation

Balancing favoring diversity

When natural selection maintains mutations

• INCREASES genetic variation

Migration

When alleles move from one population to another

• Increases diveristy

Classical school

Natural selection decreases diversity

Balance school

Natural selection increases diversity

What does the corn experiment show

There is a lot of variation, BUT most of it is probably deleterious (goes down if unchecked)

Neutral theory

Most mutations/variations are neutral (silent mutations)