Question

In the iris, leaf size is determined by 2 alleles. The genotype PP has large leaves; Pp produces medium leaves, and pp has small leaves. A cross was made between two plants each of which has medium leaves. Of the 80 progeny produced, how many had large leaves?

Answer 1

Among the 80 progeny from two Pp (medium leaf size) parental iris plants, 20 are expected to have the PP genotype, which produces large leaves, following Mendelian genetics principles.

Step-by-step explanation:

We start with two parent plants with medium leaves, which indicates that they both have the genotype Pp (heterozygous). When these Pp plants are crossed, their offspring have possible genotypes PP, Pp, and pp in a classic Mendelian 1:2:1 ratio. The PP genotype produces large leaves, Pp results in medium leaves, and pp in small leaves. In the Mendelian 1:2:1 ratio, one-quarter of the offspring are expected to be PP or have large leaves. As such, out of 80 progeny, one-quarter (or 1/4) would be expected to exhibit the large leaf phenotype. Calculating this, 1/4 of 80 is 20. Therefore, 20 out of 80 progeny would be expected to have large leaves. This straightforward calculation is an application of the Mendelian principles of genetics, which can be visualized using a Punnett square to predict the outcome of crosses based on parental genotypes.