Random union of gametes

• Let us suppose the two alleles of a gene are A and a, their frequencies are p and q respectively and that A and a gametes unite at random to yield zygotes.

Suppose, genotype of gamete   A      a

              Frequency of gamete   p       q

Random union of gametes will yield

• These union will yield the genotypes AA, Aa and aa and the frequencies of these genotypes will be p², 2pq, q²
• Each individual of population is assumed to produces equal no. of gametes say 1.
• Since, the formation of gametes is either A or a, so chance is 1.

p² + 2pq + q² = 1

(p+q)² = 1

Hence, p+q = 1

Thus, size of population is also 1.

Frequency of A gametes = All the gametes from AA+ 1/2 the gametes from Aa = p² + 1/2 (2pq)

                                        = p² + pq = p(p+q) = p [ p+q =1]

Frequency of a gamete will be = All the gamete from aa + 1/2 gametes from Aa = q² + 1/2 (2pq)

                                                 = q² + 1/2 (2pq) = q² + pq = q( p+q) = q [ since, p+q = 1]