Hardy-Weinberg Principle

Name the conditions needed to apply the Hardy-Weinberg principle:

- The population is large

- Mating within the population is random

- Population is isolated

- There are no selection pressures

- No mutations arise

Hardy-Weinberg principle equations (these are given in the exam)

p + q = 1

p² + 2pq + q² = 1

p + q = 1

p² + 2pq + q² = 1

What do each letter mean?

p = frequency of the dominant allele (e.g. all the R)

q = frequency of the recessive allele (e.g. all the r)

p² = frequency of the homozygous dominant genotype (e.g. all the RR)

2pq = frequency of the heterozygous genotype (e.g. all the Rr)

q² = frequency of the homozygous recessive genotype (e.g. all the rr)

36 out of 400 plants are dwarf (recessive phenotype).

Calculate the frequency of the tall gene.

Determine the number of heterozygous pea plants.

q² = 36/400 = 0.09

q = √0.09 = 0.03

p = 1-0.3 = 0.7

p² = 0.49

2pq = 2x (0.7 x 0.3)

2pq = 0.42