Suppose you isolated a new phenotype in mice which you name elmo, because it res

Question

Suppose you isolated a new phenotype in mice which you name elmo, because it results in mice with reddish hair and an orange nose. True breeding stocks have been established where both males and females have reddish hair and an orange nose. In preliminary results of interbreeding elmo mice and wildtype mice, male mice seem more likely to have the elmo phenotype of reddish hair and an orange nose. Two hypotheses were proposed to explain these initial observations: The elmo allele is a recessive sex linked trait and therefore males are more likely to show the phenotype of the recessive allele. The elmo trait is a sex influenced trait, heterozygous males have the elmo phenotype but heterozygous females have wildtype coloring. Describe a reciprocal cross experiment to distinguish between these two hypotheses. What results would support hypothesis I? What results would support hypothesis II? Explain how a mutation would affect the regulation of the yeast gal system if a mutation occurred in any of the following components:

Explanation / Answer

Reciprocal cross is carried out to determine the role of the sex of a parent in an inheritance pattern.

a. To determine whether a hypothetical allele P, a variant of some gene A, is on the male or female sex chromosome, the P-trait female is crossed with an A-trait male. The offsprings are observed. After this, an A-trait female is crossed with a P-trait male and the offsprings are observed. Through principles of dominant and recessive alleles, and after cross-breeding the offspring as well, an inferenance can be made as to which sex chromosome contains the gene P.

b. In sex linked traits, more males (XY) develop these triats than females (XX).

c. Sex-influenced traits are autosomal traits. Male needs one recessive allele to show that trait. Female needs two recessive alleles to show that same trait.

Reciprocal cross following two generations helps in determining the mode of inheritance of the trait.

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