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4 February, 04:56

Suppose you cross a pure-breeding, black-coated dog with curly fur to a pure-breeding, yellow-coated dog with straight fur. In the F1 generation, all the puppies have straight, black coats. Next, you interbreed the F1 dogs with one another to get an F2 generation.

If coat color and coat texture are controlled by two genes that assort independently, what fraction of the F2 puppies are expected to have yellow, straight fur?

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  1. 4 February, 05:53


    - Coat color and coat texture are controlled by two independent genes

    -The parental generation is pure breeding, meaning that individuals are homozygous for all genes.

    -The F1 was homogeneous with straight black coats, meaning that straight fur and black coats are the dominant traits.

    I will call the alleles:

    Black coat: BB or Bb Yellow coat: bb Straight fur: SS or Ss Curly fur: ss

    Parental generation cross:

    BBss X bbSS




    The expected proportions in the offspring resulting from a dihybrid cross with independent genes is 9:3:3:1, where:

    9 B_S_ black straight coats 3 B_ss black curly coats 3 bbS_ yellow straight fur 1 bbss yellow curly fur

    So 3/16 dogs of the offspring will have yellow, straight fur.
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