In the laboratory, when the heterozygous gray long-winged female flies were repeatedly crossed, the Drosophila flies had a black short-winged male. Determine the genotype of parents and offspring. Explain the cause of the four phenotypic groups of individuals.
Consider the genotypes of parents. If in the state of heterozygosity the females showed signs of “gray color” and “long wings”, it would be logical to assume that the black short-winged male is homozygous for recessive signs “black” and “short wings”, then we have the following
females – AaBb, male – aabb.
gametes given by the female: AB Ab aB ab. One male gamete – ab.
Then we will have the following variants of offspring: AaBb – gray long-winged, Aabb – gray short-winged,
aaBb – black long-winged, aabb – black short-winged. So, females are digeterozygous, the male is homozygous for recessive traits.
The reason for the manifestation of the phenotype discrepancy in the offspring is the heterozygosity of the females, because their recessive traits got a chance to appear when they are crossed with a male homozygous for these traits
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