Round seeds (R)is dominant to wrinkled seeds (r), and yellow seeds (Y)is dominant to green seeds (y).A plant of unknown genotype is testcrossed to a true-breeding plant with wrinkled and green seeds.The offspring produced were 53 round and yellow, 49 round and green, 44 wrinkled and yellow, 51 wrinkled and green.What is the likely genotype of the parent in question?
A)RRYY
B)RrYY
C)RRYy
D)RrYy
E)rryy

Question

Quizplus · Accepted Answer

First, we can determine the genotype of the true-breeding plant with wrinkled and green seeds, which must be rrYY. This is because it only produces offspring with wrinkled and green seeds when crossed with the unknown plant, indicating that these traits are both homozygous recessive in that parent.

Next, we can use the data from the offspring to deduce the genotype of the unknown parent. We know that 53 offspring have round and yellow seeds, which can only occur if the unknown parent contributes at least one dominant R and one dominant Y allele. We also know that the other 144 offspring (49+44+51) have either wrinkled or green seeds, indicating that the unknown parent must be heterozygous for both of these traits.

Therefore, the most likely genotype of the unknown parent is RrYy.

Round Seeds (R)is Dominant to Wrinkled Seeds (R), and Yellow