B1. The Hardy-Weinberg Principle

Question 1

A species is defined as

Answer 1

a group of similar organisms that can reproduce to give fertile offspring

Question 2

A population is

Answer 2

is a group of organisms of the same species living in a particular area at a particular time-so they have the potential to interbreed. Species can exist as one or more populations, eg, there are populations of the American black bear (Ursus americanus) in parts of America and in parts of Canada.

Question 3

The gene pool is

Answer 3

allele occurs in a population is called the allele frequency. It’s usually given as a percentage of the total population, eg, 35%, or a decimal, e.g. 0.35.

Question 4

The Hardy-Weinberg prediction is only true under certain conditions: (2 things)

Answer 4

• It has to be a large population where there’s no immigration, emigration, mutations or natural selection (see page 405).
• There needs to be random mating-all possible genotypes can breed with all others.

Question 5

Allele frequency equation is

Answer 5

p+q=1
p = the frequency of one allele (usually the dominant one)
q=the frequency of the other allele (usually the recessive one)

Question 6

Genotype frequency equation is

Answer 6

p² + 2pq + q² = 1

Assuming p is dominant, and q is recessive,
then p2= frequency of homozygous dominant genotype
2pq=frequency of heterozygous genotype
q2=frequency of homozygous recessive genotype