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In Drosophila, sepia colored eyes are due to a recessive allele s and wild type (red eye color) to its dominant allele s+. Sepia-eyed females are crossed to pure wild type males. What phenotypic and genotypic ratios are expected if the F1 males are then backcrossed to sepia-eyed parental females?

  • Bio -

    I'm assuming that eye color is sex-linked.

    X^s+= dominant
    X^s= recessive

    The P1 generation:
    Male: X^s+, Y
    Female: X^s, X^s

    P1 generation cross: [X^s, X^s] x [X^s+, Y]

    F1 generation
    1/2-X^s, X^s+
    1/2-X^s+, Y

    Cross of F1 males with P1 females:[X^s, X^s] x [X^s, Y]

    F-2 generation:
    1/2-X^s, X^s
    1/2-X^s, Y

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