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Homework Help: Genetics Problem Question

  1. Dec 4, 2006 #1
    ok i have this question for homework, can anyone help me?

    A man's maternal grandmother had normal vision; his maternal grandfather was colour-blind;his mother is colour-blined;his father has normal vision. Calculate the genotypes of the two parents and grandparents mentioned? What type of vision has this man himself? His sister?

    Thanks xD
     
  2. jcsd
  3. Dec 5, 2006 #2

    iansmith

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    You have to show us that have tried to solve the problem before we can help you.

    Here a few questions to get you started:
    Is colour blindness dominant or recessive, is heredity linked to any specific trait?
    Can you do a punnet square for the maternal grandparent and the mother?
     
  4. Dec 5, 2006 #3
    yea we use dat punnet square
     
  5. Dec 5, 2006 #4

    iansmith

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    Do you know if color-blind is a recessive or dominant trait and if it is linked to any other trait (i.e. the sex/X and Y chromosome)?

    this information is crucial for the punnet square.
     
  6. Dec 5, 2006 #5
    this is how i did it, its starts at question 2
     

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  7. Dec 5, 2006 #6

    iansmith

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    Colour blindness is a recessive trait and therefore a female colour blind must be homozygous recessive and have both XrXr. A normal woman will be either homozygous dominant or heterozygous (XRXR or XRXr)

    Furthermore the gene is absent on the Y chromosome. So a colour blind man is XrY and a normal individual is XRY

    You may want to redo the problem.
     
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