In cats the genotype BB is black, Bb is tortoise shell, and bb is yellow. The gene is on the x chromosome. A tortoise shell female is crossed with a black male. What offspring would be expected?...

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In cats the genotype BB is black, Bb is tortoise shell, and bb is yellow. The gene is on the x chromosome. A tortoise shell female is crossed with a black male. What offspring would be expected? Would you expect to find any tortoise shell male?

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To know the possible genotype of the offspring, we should use the punnet square.

Parents:

Male `X^B Y`

Female `X^B X^b`

                   `X^B`         `Y`

`X^B`     `X^BX^B`    `X^BY`

`X^b`     `X^BX^b`      `X^bY`

 

Results:

25% Black males

25% Yellow males

0% Tortoise shell male

25% Black female

25% Tortoise shell female

0% Yellow Female

 

It would be very rare to find a tortoise shell male because tortoise shell can be only achieved if there are two X chromosomes. If that happens, there will be an unequal number of gametes. The resulting genotype would be `X^BX^bY` which is apparently abnormal.

 

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