Suppose Stephen breeds snakes and wants to optimize production of offspring with both black bodies and brown eyes, which are coded for by two genes with the recessive alleles b and e, respectively. In snakes, B codes for brown bodies and E codes for red eyes. Stephen crosses two heterozygotes that produce 544 offspring. How many of these 544 offspring are predicted to have both black bodies and brown eyes?

34

Explanation:

B codes for brown bodies.

E codes of red eyes.

b and e together code for black bodies and brown eyes.

Heterozygous brown body snake would have the genotype Bb.

Heterozygous red eyes would have the genotype Ee.

Individuals that are heteozygous for both trait would have the genotype BbEe.

Crossing two heterozygous individuals:

BbEe   x   BbEe

Progeny:

9 BBEE

3 B_ee

3 bbE_

1 bbee

Recall that black bodies and brown eyes requires be, hence the ratio of the progeny with black bodies and brown eyes is 1/16.

If the total number of offspring produced is 544, the number predicted to have black bodes and brown eyes would be:

    1/16 x 544 = 34

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