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    In an exam question when it asks you to write out the pheno types, genotypes and gametes of male and female to determine the sex.
    When you do the female gamete do you draw X X ( both in a circle) for the female gamete or just write X(in a circle).
    It matters because when u do the punnet square it will be drawn as
    X*XY which will results in XX and XY whereas with two female gametes it’s XX*XY which will give four answers: XY,XY,XX,XX. I know they both give 50/50 of the gender but I don’t wanna do the wrong one in my exam (IGCSE Biology Edexcel A*-G) . If u know please help
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    You only draw one X gamete as per convention. The final answer is not affected because the ratio of boys (XY) to girls (XX) is the same, regardless of whether you started with one or two X's.

    Similarly, if you are drawing a punnet square for the inheritance of say sickle cell anaemia and the mother is homozygous for the sickle cell allele, then you would only draw 1 HbS gamete from the mother because she can only produce 1 type of gamete.
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    (Original post by Keira Larkin)
    You only draw one X gamete as per convention. The final answer is not affected because the ratio of boys (XY) to girls (XX) is the same, regardless of whether you started with one or two X's.

    Similarly, if you are drawing a punnet square for the inheritance of say sickle cell anaemia and the mother is homozygous for the sickle cell allele, then you would only draw 1 HbS gamete from the mother because she can only produce 1 type of gamete.
    Ahhh thank you- the last part would it make a difference putting two HbS?sorry for pestering
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    (Original post by standardproduct)
    Ahhh thank you- the last part would it make a difference putting two HbS?sorry for pestering
    If you were to draw the Punnet square with one or two HbS gametes, you would still get exactly the same ratio for all the genotypes. Draw the Punnet squares and see this for yourself.
 
 
 
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