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    Cross breeding

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    Vanessa has obtained two true-breeding strains of mice, each homozygous for an
    independently discovered recessive mutation that prevents the formation of hair on
    the body. The discoverer of one of the mutant strains calls his mutation "naked," and
    the other researcher calls her strain "hairless." To determine whether the two
    mutations are simply alleles for the same gene, Vanessa crosses naked and hairless
    mice with each other. All the offspring are phenotypically wild-type. After
    intercrossing these F1 mice, however, Vanessa observes 115 wild-type mice and 85
    mutant mice in the F2.

    (a) Are the naked and hairless mutations alleles for the same gene?

    (b) Using these symbols:
    n = naked mutation, N = wild-type allele, h = hairless mutation, H = wild-type allele
    Indicate the genotypes of the parents, the F1, and each of the phenotypic classes of
    the F2 progeny. Describe any gene interactions in this set of crosses.
    i. parental genotypes: _ ___________________
    ii. F1 genotypes: ________________________
    iii. F2 Genotypes Phenotypes
    F2 genotype ratio: _______________________
    F2 phenotype ratio: ____________________
    66-X143 Final Examination

    (c) What is the most likely explanation for the segregation of wild type and mutant
    mice in the F2?

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    Solution Preview

    Hi there,

    Thanks for letting me work on your post. Here is my explanation:

    (a) since all F1 offspring are phenotypically wild type, the ...

    Solution Summary

    The expert determines if naked and hairless mutations alleles are for the same gene.