Imagine you have two pure-breeding lines of canaries, one with yellow feathers and the other with brown feathers. in crosses between these two strains, yellow female x brown male gives only brown sons and daughters, while brown female x yellow male gives only brown sons and yellow daughters. propose a hypothesis to explain these results.

The results can be explained if the gene that determines color of feathers is located in the Z chromosome.

Explanation:

Unlike mammals that have X and Y sex chromosomes, birds have Z and W sex chromosomes. Females are ZW and males are ZZ.

The gene that determines color of feathers has the alleles:

B_ = brown color

bb = yellow color.

yellow female  x   brown male

Gametes

Female: ,

Male:

brown female   x   yellow male

Gametes

Female: ,

Male:

the answer to your question is sperm