Question

The mutant strain maroon-like has an X-linked mutant allele (Xm) that results in deep maroon-colored eyed in homozygous females and hemizygous males. To prove to a skeptical friend that this trait is in fact X-linked you set up a reciprocal cross against the wild type. What are the expected genotypic and phenotypic frequencies of each half of this crossing experiment?

Answer 1

Answer:

See the answer below

Explanation:

From the illustration, maroon-like mutant strain is represented by the allele m and it is X-linked. Homozygous females ($X^mX^m$) and hemizygous males ($X^mY$) have the maroon trait and are mutants.

A reciprocal cross is made against the wild type. The wild type would be homozygous for the alternate from of the gene in females and hemizygous for alternate form of the gene in males.

Crossing a wild type female with a mutant male (first half);

$X^MX^M$   x   $X^mY$

Progeny = $X^MX^m, X^MX^m, X^MY, X^MY$

Genotypic ratio: 1 $X^MXm$ : 1 $X^MY$

Phenotypic ratio: All wild type

Crossing a mutant female with a wild type male (second half);

$X^mX^m$   x   $X^MY$

Progeny = $X^MX^m, X^MX^m, X^mY, X^mY$

Genotypic ratio: 1 $X^MX^m$ : 1 $X^mY$

Phenotypic ration: 1 wild type : 1 mutant