In pumpkin, the white color of the fruit (A) dominates over the yellow (a), and the disc-shaped form of the fruit (B) over the spherical (c). When a pumpkin, which has white disc-shaped fruits, is crossed with a pumpkin that has the same characteristics, individuals were found in the offspring that form yellow spherical fruits. Determine the genotypes of the parents, the phenotypes of the offspring and the likelihood of the appearance of pumpkins with white disc-shaped fruits (assuming an independent distribution of traits).
Since the progeny of these pumpkins produced plants with recessive traits and the corresponding genotype aavb, it should be concluded that the parental individuals are heterozygous for the genes of both traits.
Let us write the parent plants as AaBb, and the germ cells produced by them as ab, AB, Ab and ab.
The offspring will be represented by the following options:
pumpkin with white disc-shaped fruits (AABB, 2AaBB, 2AABb, 4AaBb);
pumpkin with white globular fruits (2Aab, AAbb);
pumpkin with yellow disc-shaped fruits (aaBB, 2aaBb);
pumpkin with yellow spherical fruits (aabb).
Pumpkins with white disc-shaped fruits account for 9 out of 16 genotypes, or 56.25% of all plants obtained.