Question

In pea plants, y confers yellow peas and y confers green peas. if you cross two heterozygous yy pea plants, what fraction of the offspring will be yellow?

Answer 1

When crossing two heterozygous yellow pea plants (Yy x Yy), 75% of the F2 offspring will display the yellow pea phenotype, because yellow (Y) is the dominant allele over green (y). A Punnett square analysis shows that three out of four combinations result in yellow peas.

Step-by-step explanation:

In classical Mendelian genetics, when two heterozygous yellow pea plants (Yy) are crossed, the offspring will exhibit a 3:1 ratio of yellow to green peas. This is because yellow (Y) is dominant over green (y). To find the fraction of yellow peas, you need to perform a Punnett square analysis.

Here, each parent can pass on either a Y (yellow) or a y (green) allele. The possible combinations for the offspring will be: YY (homozygous dominant), Yy (heterozygous), Yy (heterozygous again), and yy (homozygous recessive). Only yy will result in green peas, while the other three combinations will result in yellow peas.

Therefore, the fraction of offspring with yellow peas is: YY + Yy + Yy = 3/4 or 75%. Hence, we can infer that there is a 75% chance of yellow pea offspring from a cross between two heterozygous yellow pea plants.