Question

Consider a gene with a dominant and recessive allele in a population conforming to the Hardy-Weinberg conditions. Assuming the frequency of the recessive allele in the entire population is q, show that the frequency of the recessive allele in individuals with the dominant phenotype is q/(1+q).

Answer 1

Answer:

• Frequency of recessive allele = q
• Frequency of dominant allele p = 1 - q
• Let the population size be = N
• Total number of alleles = 2N
• Total number of dominant alleles = p*2N + p*q*2N
  Total number of heterzygous individuals = 2*p*q*2N
• Number of recessive allele in dominant phenotype = 1/2 *(2*p*q*2N) = p*q*2N
• Therefore, Frequency of recessive alleles in dominant phenotype =
• Number of individuals with recessive alleles in dominant phenotype / Total number of dominant phenotypes
• = (p*q*2N) / (p*2N + p*q*2N)
• = p*q / (p + p*q)
• = p*q / [p*(1 + q)]
• = q / (1 + q)
• Therefore, requency of the recessive allele in individuals with the dominant phenotype = q/(1+q).