1) What will the genotype frequencies be in a population that has two alleles, o

Question

1) What will the genotype frequencies be in a population that has two alleles, one with a frequency of 30% (p = 0.3)?

2) A human blood group, related to the MN system, is also controlled by two alleles (S and s), and three distinct phenotypes can be identified by means of the appropriate reagents. In a sample of 1000 people, the number of different genotypes were as follows: 99 SS, 418 Ss, and 483 ss. Estimate the allele frequency of S (p) and s (q) and carry out a Chi square test of goodness of fit between the observed genotype frequencies and their Hardy-Weinberg expectations. Is there any reason to reject the hypothesis of Hardy-Weinberg proportions for this gene?

3) The h allele is a recessive allele that causes blindness in homozygous recessive individuals. If the frequency of recessive homozygotes in a population is 1%, then what are the allele frequencies? What are the frequencies of heterozygotes and of dominant homozygotes?

Explanation / Answer

Hardy and Weinberg also described all the possible genotypes for a gene with two alleles. The binomial expansion representing this is, p2 + 2pq + q2 = 1.0; (p+ q = 1)

Where,

p2 = proportion of homozygous dominant individuals

q2 = proportion of homozygous recessive individuals

2pq = proportion of heterozygotes.

Given that, p = 0.3, q = 1-0.3 = 0.7.

Now, the frequency of population with homozygous dominant allele = p2 = 0.09

The frequency of population with heterozygous alleles = 2pq = 0.42

The frequency of population with homozygous recessive alleles = q2 = 0.49

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