7.2 population genetics and errors

Population

A group of organisms belonging to the same species found in the same area at the same time

That can potentially interbreed

Allele frequency

How often an allele of a gene occurs in a population

Gene pool

All alleles in a population

Identifying genotype of dominant phenotype

Cross with a homozygous recessive

Presence of recessive phenotype in offspring identifies heterozygous genotype in the parent

What the hardy-Weinberg principle predicts

Looks at allele frequency within populations

Predicts that the frequency of the allele of a gene in a particular population will stay the same from generation to generation

5 conditions where hardy Weinberg principle is valid

• population is large

• No immigration or emigration

• all genotypes have equal reproductive success

• Mating is random

• No gene mutation.

Hardy Weinberg equations

p² + q² + 2pq = 1

p + q = 1

why is there a time lag between the introduction of pesticide and appearance of the first inspect species to the pesticide (3)

1. Initially one / few insects with favourable mutation / allele;

2. Individuals with (favourable) mutation / allele will have more offspring;

3. Takes many generations for (favourable) mutation / allele to become the most common allele (of this gene).

HOW TO CONCLUDE SPECIES ARE SEPERATE (2)

1. (Compare DNA) base sequence / base pairing / (DNA) hybridisatio

2. Different in six (species) /different in different species / similar in three (subspecies) similar in same species/subspecies

types of selection (3)

1. disruptive

2. directional

3. stabilising