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Last bio question

  1. Feb 19, 2006 #1
    7. Hand in question: Suppose that an allele, d, of a sex-linked gene is recessive and lethal. A man marries a woman who is heterozygous for this gene. If the couple had many normal children, what would be the predicted sex ratio of these children?

    Female: XDXd

    Male: XDY

    Punette sqaure:

    XD Xd
    XD XD XD XD Xd
    Y XD Y Xd Y

    1: XD XD : 1 XD Xd : 1 XD Y : 1Xd Y

    XD XD , XD Xd : 100% normal female

    XD Y , Xd Y : 50% normal male, 50% letal
  2. jcsd
  3. Feb 19, 2006 #2


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    Staff Emeritus
    Science Advisor
    Gold Member

    So far your work looks fine, but they're asking for the sex ratio, which means the ratio of male:female offspring (or female:male, it doesn't matter which way you represent it, as long as you specify). You have all the information you need to find this based on the work you've already done.
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