Question

A plant has two alleles for color. The red allele is recessive and is represented by q. The purple allele is dominant and is represented by p. If 30 of 100 organisms are red, what is q?. p^2+2pq+q^2=1. A. 0.55. B. 0.30. C. 0.49. D. 0.70

Answer 1

We are given with two alleles for color: one is the red allele and the other is the purple allele. The equation that represents the two alleles is expressed  p^2+2pq+q^2=1. We are given with 0.30 probability for the red allele. we substitute this to the equation to determine the purple allele probability, q. The answer is D. 0.7 

Answer 2

If 30/100 organisms are red (have a red phenotype), this only occurs if it has the qq allele, which has probability q². This implies that q² = 0.3, and q = √0.3 = 0.55.
The rest of the possible genotypes: pp, pq, and qp, would all result in a purple appearance, since p is the dominant allele.