Question

You have mated a red-eyed female fly of the genotype CcaXw+Xw-e to an eosin eyed male of the genotype CcaXw-eY. Which F1 genotype does not correspond to a red-eyed female?

a)CcaXw+Xw-e
b)CCXw+Xw-e
c)CcaXw-eXw-e
d)cacaXw+Xw-e
1)red eyed female
(CcaXw+Xw-e)
2)eosin eyed male
(CcaXw-eY)
3)cream eyed male
(cacaXw-eY)
4)red eyed male
(CcaXw+Y)

Answer 1

The genotype CcaXw-eXw-e does not correspond to a red-eyed female because it lacks the dominant allele Xw+ necessary for red eyes; the genotype indicates eosin eyes.

Step-by-step explanation:

A student has asked which F1 genotype does not correspond to a red-eyed female, given a cross between a red-eyed female fly with genotype CcaXw+Xw-e and an eosin eyed male of genotype CcaXw-eY. The genotypes given in the question are a bit unconventional, as they seem to combine autosomal alleles (C and ca for body color) with the sex-linked eye color alleles (Xw+ for red eyes, Xw-e for eosin eyes), which is not typical in Drosophila genetics. Normally, we consider eye color to be an X-linked trait in fruit flies, with red eyes (Xw+) being dominant to white eyes (Xw). However, given the info provided, the correct answer to the question would be CcaXw-eXw-e, as the F1 female with this genotype would not have the Xw+ allele necessary for red eyes. The genotype corresponds to choice (c), indicating that females with this makeup are not red-eyed but instead have eosin eyes.