Question

In garden peas, purple flower color is dominant to white flower color. In a population of 500 pea plants, 180 of them are white and 320 of them are purple. How many white flower alleles are present in this population?

• A. 80
• B. 210
• C. 240
• D. 310
• E. 120

Answer 1

Answer: (D)

310

The plants with purple flowers are 320 (p${}^2$ +2pq) and with the white flowers are 180 (q${}^2$). So, the recessive allele is

q${}^2$=180=0.18

q=0.42

Since, p+q=1, so, p=0.58

The purple allele is dominant on white so the heterozygous plants will also have the white alleles.

So, white alleles= q + 1/2(2pq)= 0.42 + 1/2(2 x 0.42 x 0.58) = 0.6216

There are total of 500 flowers, so, 0.6216 x 500=310.

Thus, the correct answer is option D.