Question

You are studying a population of snapdragon plants on Membata Island. In snapdragons, the dominant allele CR encodes red flowers and the recessive allele CW encodes white flowers. Plants with a heterozygous CRCWgenotype have pink flowers. You have counted 10,000 snapdragon plants on Membata Island. You have recorded that 9025 plants have red flowers, 950 plants have pink flowers, and 25 plants have white flowers. If this population is at a Hardy-Weinberg equilibrium, what are the values of p and q in this population? Show your calculations.

Answer 1

According to Hardy-Weinberg equilibrium sum of all the allelic frequency of a gene is always 1 and sum of all the genotypic frequency of all the genotype is always 1.

So p+q =1

p2+ 2pq+q2 =1

Let R be the allele for Red flower and r be the allele for white flower.

here p = frequency of R allele

q is the frequency of r allele.

p2 frequency of RR genotype

q2 frequency of rr genotype

2pq frequency of Rr genotype

Given that out of 10000 plants 25 plants were a white-flowered plant.

So frequency of white flower plant = 25/10000 = 0.0025.

White flower is due to rr genotype.

So, q2 = 0.0025

q = 0.05.

Also p+q =1

so p = 1-0.05

or p = 1-0.0.05

Hence p =0.95

So value of p is 0.95 and q is 0.05.

So frequency of R allele is 0.95 and r allele is 0.05

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