Chapter 25 Test 4 genetics

Population genetics

Study of genetic variation in populations and how it changes over time

Population

Group of organisms of the same species that live in the same area and interbreed

Generations

Sequential groups linked by reproduction and inheritance

Allele

A version of a gene

Genotype

The combination of alleles an organism has

Genetic structure of a population

Described by allele and genotype frequencies

Genotypic frequency

Proportion of individuals with a specific genotype

Allelic frequency

Proportion of a specific allele in a population

Allele frequency formula

Number of copies of allele ÷ total number of alleles

p and q

Symbols used to represent allele frequencies

p + q = 1

Sum of allele frequencies equals 1

Genotypic frequency calculation

Number of individuals with genotype ÷ total individuals

Allele frequency from genotype

Can be calculated using genotype counts

Evolution (population genetics)

Change in allele frequencies over generations

Hardy

Weinberg equilibrium

Hardy

Weinberg conditions

Random mating

Individuals pair by chance, not based on genotype

Hardy

Weinberg equation

p²

Frequency of homozygous dominant genotype

2pq

Frequency of heterozygous genotype

q²

Frequency of homozygous recessive genotype

AA frequency

Equal to p²

Aa frequency

Equal to 2pq

aa frequency

Equal to q²

Meaning of equilibrium

No evolution is occurring

Forces that disrupt equilibrium

Natural selection, non

Recombination frequency (context)

Helps estimate genetic relationships (from earlier concepts)

Example allele frequencies

If p = 0.7, q = 0.3

Example AA frequency

0.49 (0.7 × 0.7)

Example aa frequency

0.09 (0.3 × 0.3)

Example Aa frequency

0.42 (2 × 0.7 × 0.3)

Codominant alleles

Both alleles are expressed (e.g., MN blood type)

MN blood group example

Used to calculate genotype frequencies