Question: In Drosophila melanogaster, eyeless (ey) is a recessive trait in which the eyes are tiny or absen…

In Drosophila melanogaster, eyeless (ey) is a recessive trait in
which the eyes are tiny or absent. The ey locus is found on
chromosome 4. Monosomy and trisomy for this very small chromosome
are compatible with survival and fertility. A trisomic wild-type
male with the genotype ey+ ey+ ey is crossed to an ey+ ey female.
Assuming random segregation of chromosomes into gametes, determine
the chromosome constitution and phenotypic ratios in the
offspring.

Helpful Hint: Use chromosome segregation in a trisomic
individual, then use the forked-line method/branching diagram to
solve the problem.