Geneticsss helpppppppp?

how many genotypes will be produced by crossing 2 alleles "a" and "A" ? N tell me. How ?

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  • Holly
    Lv 7
    8 years ago
    Favorite Answer

    I think you're asking if you crossed parents with Aa and Aa genotypes, what would come out of it?

    Ok, let's assume that this is for hair color, and brown is dominant, blonde is recessive.

    AA = brown

    Aa = brown

    aa = blonde

    Use a punnet square:

    .....A....a

    A. AA Aa

    a .Aa aa

    So, if you cross Aa and Aa, you will get the following genotypes:

    25% AA

    50% Aa

    25% aa

    So that means that 25% of the offspring with have the homozygous dominant phenotype, 50% will have the heterozygous dominant phenotype, and 25% would have the homozygous recessive phenotype.

    So 75% of the offspring would have brown hair

    25% would have blonde hair.

  • 8 years ago

    Doesn't make sense. Genes each have 2 alleles. So do you mean crossing an aA with an aA?

    By having just two alleles, you would have one genotype - aA.

    Crossing aA and aA you wouldget 3 genotypes - aa, AA, and aA

  • 8 years ago

    genes have 2 alleles

  • Anonymous
    8 years ago

    for aa & AA = only Aa

    for aa & Aa = Aa & aa

    you should have to say more details

    Source(s): sounds like you are still in grade 4 /5
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