Joe has a white cat named Sam. When Joe crosses Sam with a black cat, he obtains 12 white kittens and 12 black kittens. When the black kittens are interbred, all the kittens that they produce are black. On the basis of these results, would you conclude that white or black coat color in cats is a recessive trait?

The question is incorrect. The correct question is as follows:

joe has a white cat named Sam. When Joe crosses Sam with a black cat, he obtains 1/2 white kittens and 1/2 black kittens. When the black kittens are interbred, all the kittens that they produce are black. On the basis of these results, would you conclude that white or black coat color in cats is recessive? Why?

Black coat color is recessive.

Explanation:

The dominant trait is the trait that has ability to express itself in homozygous as well as in the heterozygous condition. The recessive trait can express itself only in the homozygous recessive condition.

The crossing of white cat with black cat will show the cross as follows:

Bb ( white) ×  bb ( black )

Bb, Bb ( white) and bb, bb (black).

The inter breeding of black kitten is as follows:

bb ( black)  ×  bb ( black )

All progeny will be bb ( black).

From the above crosses it is clear that black is recessive trait.

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