bio ch 20

Genetic variation

Difference in alleles, phenotype or genotype among individuals in population

Mutations

Random changes in DNA sequences resulting in New alleles

recombination

Shuffles mutation to create new alleles

Why is genetic variation important?

It is required for all evolutionary change.

What are the 3 ways allele/genotype frequencies are measured?

Observable traits, protein electrophoresis, DNA sequencing.

What is evolution?

change of allele frequencies in a population over time

What is Hardy–Weinberg equilibrium?

under certain conditions, no evolution will happen

What are the 5 conditions for HWE?

No mutation, no migration, no natural selection, no genetic drift, no sexual selection

What happens to allele frequencies under HWE?

They remain constant across generations.

What does it mean if an allele is fixed?

its frequency is 1 (only allele in pop)

What does it mean for an allele to be lost

its frequency is 0 (allele dissapeears)

What are the 3 requirements for natural selection?

variation, heritability, best fit

How does natural selection affect allele frequencies?

avantageous alleles increase,

delterious alleles decrease

what leads to adaptation

Variation → Heritability → Selection → Adaptation

What is an adaptation?

A trait that increased fitness

directional stabilization

One extreme phenotype is favored;

one extreme over the other

What is stabilizing selection?

Intermediate phenotype favored;

selects against both extremes

What is disruptive selection?

Both extremes favored;

selects against intermediate

what is Genetic drift?

random changes in allele frequencies

what is the source of genetic variation

mutations and recombination

What is evolution by natural selection?

differential survival and reproduction based on heritable traits

non adadptive evolution

changes in allele frequencies not due to fitness

• mutations

• genetic drift

• gene flow

alleles

diff versions of a gene

genotype

genetic makeup (aa, AA, Aa)

phenotype

physical traits