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Biology Punnet Square Question

  1. Oct 26, 2012 #1
    1. The problem statement, all variables and given/known data

    The Xolo is the national dog of Mexico. The striking characteristic of this dog is that it
    has no hair. Xolos carry a mutation in Chromosome 17 that, when homozygous, is lethal.

    If two hairless Xolos were mated, what fraction of their surviving offspring would be hairless?


    2. Relevant equations



    3. The attempt at a solution

    If two hairless Xolos were mated, assuming Hh and Hh since homozygous would not exist, then 1/4 would be HH 1/4 would be hh and these would die because they're homozygous. and 2/4 Hh.

    Therefore 50% would have no hair. But the answer is 2/3 will have no hair, why?
     
  2. jcsd
  3. Oct 27, 2012 #2

    AGNuke

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    Gold Member

    I think HH should be lethal and not hh because it is the dominant Chromosome 17 trait, while h is its recessive counterpart (meaning that Xolos must have hair), it should not be lethal when present as hh.

    So, HH will die, so 2 Hh will not have hair, while hh will have hair. So, answer's 2/3.
     
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