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Thread: Pedigree Analysis

  1. #1 Pedigree Analysis 
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    I have a problem which corresponds to the pedigree analysis. There is a disease which is inherited by X-linked recessive. The problem is that the father is affected (XaY) and the mother is homozygote (XAXA). They have 4 children, 2 sons and 2 daughters. The sons are not affected (XAY) and one of the daughter is a carrier (XaXA). The other daughter is not affected. The problem is that she should be affected but she isnīt. What could be the possible cause of that??


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  3. #2  
    Forum Cosmic Wizard i_feel_tiredsleepy's Avatar
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    Mommy's sleeping with the postman.

    Also, the daughter who is XaXA should be a carrier, not affected.

    I think you should reread the question. I think the mother may be heterozygous if that's the right phenotype for the children. Maybe the question reads that the mother is unaffected, not homozygous for the wt allele.


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  4. #3  
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    Iīve corrected that.
    Iīve read that again and thatīs the situation. Probably there had to be some sort of mutation that caused the girl to be not affected. But what king of mutation could cause that??
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  5. #4  
    Forum Cosmic Wizard i_feel_tiredsleepy's Avatar
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    If that really is the case and the mother is homozygous for the wt. Then you could theoretically have a mutation that would revert the allele from the father back to the wt. However, the much more likely situation is that he is not the father of the fourth daughter.

    If you have XaY x XAXA

    Then the only possibilities for sons is XAY so all boys should be unaffected.

    The possibilities for daughters is 100% XaXA

    If you have a father XaY x a mother who is XaXA

    Then you could have 1/2 XaY and 1/2 XAY

    Daughters: 1/2 XaXA and 1/2 XaXa

    The only possible way to get a daughter who is XAXA is with a father who is XAY
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