Loppins are fictitious (but useful) diploid invertebrates that produce large off

Question

Loppins are fictitious (but useful) diploid invertebrates that produce large offspring and normally have long antennae. Short antennae mutants also exist. Unfortunately for the geneticists working on these organisms, the males’ antennae don’t fully develop until the loppin equivalence of “middle age.” A female with short antennae is crossed to a young male, and all the females in their offspring have the short antennae mutant phenotype. A subset of these F1 females are crossed to a middle-aged male with short antennae, and all the females produced by these crosses have short antennae. However, all the crosses between the F1 females and their brothers produce both short antennae and long antennae loppins in a ratio of about 3:1. How can these results be explained? Provide the genotypes of as many individuals as possible.

Explanation / Answer

Since they have produced both short antennae and long antennae loppins in the ratio of 3:1 it shows that the genes for antenna segregate independently. But their genes are epistatic with respect to male hence they grow after a age where they gain loppin equivalence.

Female with short antenna (aa) Young male (AA) short antenna is dominant over long ones, The cross will yield the following genotype, Aa, Aa, Aa, Aa - Since short antenna is dominant all the F1 offspring were having short antenna.

F1 females with their brothers Aa X Aa - AA, Aa, Aa and aa - Hence 3:1 ratio for length of antenna.

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