The Chinese Alligator Alligator sinensis above is a critical

The Chinese Alligator (Alligator sinensis; above) is a critically endangered species living in a restricted reserve area in the Yangtze River in China’s Anhui province. (Captive populations are doing much better; where individuals may live up to 70 years).

b)Assume there is a Mendelian trait determined by two alleles, A and a. The allele frequencies in the population are A=0.8, a=0.2. Assuming that there is no immediate selection on this trait, what are the genotype frequencies in a population of 500 individuals? How many individuals with each genotype are there?

Solution

The total number of alleles in the population -----> 500 x 2 = 1000

Mendelian trait determined by two alleles, A and a so that as per Hardy-Weinberg principle,

p 2 + 2pq + q 2 = 1                                  

p ^2 = (0.8)^ 2 = 0.64, now the number of individuals with genotype (AA) = 1000 * 0.64 = 640

2pq = (0.8)(0.2) = 0.16, now the number of individuals with genotype (Aa) = 1000 * 0.16 = 160

q 2 = (0.2)^ 2 = 0.04 now the number of individuals with genotype (aa) = 1000 * 0.04 = 40