Suppose that true-breeding (homozygous), black female dogs are mated with true-breeding (homozygous) brown male dogs. The F1 generation offspring are all black – 6 females and 5 males. The F1 offspring were mated with one another, and there were 15 black females, 7 black males, and 8 brown males in the F2 generation.

Question

Suppose that true-breeding (homozygous), black female dogs are mated with true-breeding (homozygous) brown male dogs.  The F1 generation offspring are all black – 6 females and 5 males.  The F1 offspring were mated with one another, and there were 15 black females, 7 black males, and 8 brown males in the F2 generation.

anonymous · Answer

b. Is this most likely an autosomal or a sex-linked trait? Explain how you can be sure? 

Autosomal are the remaining pairs of chromosome that are found in both sexes, while sex-link are genetic traits on the X and Y chromosome since they tend to characterize one sex from another.

I believe it is sex-linked because there are more females born with the black coat then brown ones.

blues · Answer

It's definitely sex linked. You know it's sex linked because in the F2 generation you see a roughly even number of brown and black males, but all the F2 females are black.

anonymous · Answer

ohhh, i see. Thank you blues!

blues · Answer

You're very welcome!

anonymous · Answer

When is it ever autosomal? if you don't mind me asking..

blues · Answer

It would be autosomal if roughly a quarter of dogs were brown and female, a quarter of dogs were black and female, a quarter of dogs were brown and male and a quarter of dogs were black and male.

anonymous · Answer

ohhh... thank you again!

blues · Answer

These crosses and Punnet squares were confusing until suddenly I had a moment of epiphany - now I really enjoy them.