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Can someone please help, so stuck!: Dihybrid cross and punnett square biology problem

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    • Thread Starter

    Complete a dihybrid cross for the following:

    Hairy monsters; homozygous for long, pinkhair were crossed with ones which were homozygous for short green hair.

    i) All of the F1 generation had short pink hair.Using punnett squares explain this result.

    ii) Calculate the probabilities for theF2 generation.
    • Thread Starter

    Please help
    • Thread Starter


    So if homozygous cross with homozygous, they all become heterozygous. Since all the F1 progeny are short + pink hair, these must be the dominant alleles.

    From this we can make the following assumptions: S = short, s = long, P = pink, and p = green. Capital letters = dominant allele.

    From here you would do a 4x4 Punnett cross with SsPp x SsPp.
    As it is a heterozygous parent, the gametes (due to containing only one allele) will have the following gene combinations: SP Sp sP sp.

    The crossing of 2 heterozygous parents also means it is a dihybrid cross, leading to a phenotypic 9:3:3:1 ratio of progeny.

    Expressing short + pink (SP): 9
    Expressing short + green (Sp): 3
    Expressing long + pink (sP): 3
    Expressing long + green (sp): 1
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