Answer and Explanation:
Available data:
- white eyes (Xe) is recessive to red eyes (XE) and is sex-linked
- hairy body (h) is recessive to hairless (H) and is autosomal
- A red-eyed, hairy male is crossed with a red-eyed, hairless female
- The female´s father was white-eyed and whose mother was hairy.
We know that the female is red-eyed and hairless. So its genotype must be XEX- H-. E is the dominant allele for the red eyes color, and H is the dominant allele for the absence of hair. The "-" symbols mean that we do not know yet if it is a dominant allele (in which case the female´s genotype for the trait would be dominant homozygous) or a recessive one (In which case the female´s genotype for the trait would be heterozygous). We must figure it out.
- The female´s father was white-eyed, which means that its genotype for the trait was XeY, because the recessive allele "e" expresses white eyes. This father showed a recessive allele for the color of the eyes.
- The female´s mother was hairy, which means that this mother was recessive homozygous for the hair trait. Its genotype was hh, because "h" is the recessive allele for the hair trait.
Both female´s parents had to give the female one allele each. This is, the female inherited one allele from each parent. As the father was recessive for the color of the ayes, which is a sex-linked gene, it gave the female the "Xe" allele. And in the same way, as the mother was recessive homozygous for the hair trait, it gave the female the "h" recessive allele.
We also know that the female is red-eyed and hairless, which means that its genotype must include the dominant forms, "XE" and "H", also inherited from the parents. So, if the father gave the female the recessive Xe form, then the mother must have given it the dominant XE form. And in the same way, if the mother gave the female a recessive allele h for hair trait, then the father must have given it the dominant form for the hairless trait, H.
This means that:
- The father´s genotype was XeY H-, with the "-" symbol meaning that we do not know if it was homozygous or heterozygous for the hair trait.
- The mother´s genotype was XEX- hh, with the "-" symbol meaning that we do not know if it was homozygous or heterozygous for the color of the ayes trait.
- The female´s genotype is XEXe Hh, heterozygous for both traits.
Cross: A red-eyed, hairy male is crossed with a red-eyed, hairless female
Parental) XEY hh x XEXe Hh
Gametes) XEh Yh XEh Yh (male)
XEH XEh XeH Xeh (female)
Punnet Square) XEh XEh Yh Yh
XEH XEXE Hh XEXE Hh XEY Hh XEY Hh
XeH XEXe Hh XEXe Hh XeY Hh XeY Hh
XEh XEXE hh XEXE hh XEY hh XEY hh
Xeh XEXe hh XEXe hh XeY hh XeY hh
F1) 6/16 red-eyed and hairless individuals in total
4/16 red-eyed and hairless females
2/16 red-eyed and hairless males
2/16 white-eyed and hairless males
6/16 red-eyed and hairy individuals in total
4/16 red-eyed and hairy females
2/16 red-eyed and hairy males
2/16 white-eyed and hairy males
2/16 females are dominant homozygous for the color of the eyes
and heterozygous for the hair trait, XEXE Hh
2/16 females are heterozygous for both traits, XEXe Hh
2/16 females are dominant homozygous for the color of the eyes
and recessive homozygous for the hair trait, XEXE hh
2/16 females are heterozygous for the color of the eyes
and recessive homozygous for the hair trait, XEXe hh
2/16 males are red-eyed and heterozygous for the hair trait, XEY Hh
2/16 males are white-eyed and heterozygous for the hair trait, XeY
Hh
2/16 males are red-eyed and recessive homozygous for the hair trait, XEY
hh
2/16 males are white-eyed and recessive homozygous for the hair trait,
XeY Hh
a. What are the genotypes of the parents?
- The father´s genotype was XeY H-
- The mother´s genotype was XEX- hh
b. What proportion of the total offspring will be Red-eyed and hairy?
6/16 red-eyed and hairy individuals in total
What proportion of the total offspring will be White-eyed and hairless males?
2/16 white-eyed and hairless males, XeY Hh
What proportion of the total offspring will be White-eyed and hairless females?
0/16 white-eyed and hairless females. All females are red-eyed