Question

In pea plants, the allele for round seeds is dominant to the allele for wrinkled seeds. at another gene locus, the allele for yellow seeds is dominant to the allele for green seeds. these two allele pairs assort independently. if a plant breeder crosses two plants that are both heterozygous at both gene loci, what percentage of the plants that produce round seeds will also produce yellow seeds? ( enter the number only without the percent sign.

Answer 1

If both parents are heterozygous for both genes, it means that we are crossing two dihybrid plants which will lead to an offspring that will present the following phenotype proportions:
Round/yellow seeds (both dominant characteristics) - 9/16
Round/green seeds (only one dominant characteristic) - 3/16
Wrinkled/yellow seeds (only one dominant characteristic) - 3/16
Wrinkled/green seeds (both recessive characteristics) - 1/16

So, to calculate what is the percentage of the plants that produce round seeds that will also produce yellow seeds, we need to consider the number of seeds that are round and yellow and divide them by the total number of round seeds. $\frac{9/16}{12/16}$=0.75 → 75%