Labrador retrievers are black, brown, or yellow. in a cross of a black female with a browrn male, results can be either all black puppies 1/2 black to 1/2 brown puppies, or 3/4 black to 1/4 yellow puppies how many genes must be responsible for these coat colors in labrador retrievers?

2

Explanation:

If all black puppies result in a mix between black and brown dog, this means that black is dominant over brown. Lets reflect B's black and b's gray.

1/2 is black and 1/2 is brown in one form of cross, i.e. 1 black:1 brown.

This type of phenotypic ratio can be found only when the black parent is heterozygous Bb and the brown parent is homozygous Bbx bb Progeny: bb (black) and bb (red) in a ratio of 1:1 Another type of 3/4 progeny is black and 1/4 white. This 3:1 ratio is typical of a cross that is monohybrid.

All parents are heterozgyous for a particular gene in the monohybrid cross, but it is not probable because the brown is a recessive trait and the brown parent can not be heterozygous.A new yellow phenotype is also produced in the offspring. This means that the 2nd gene affects the color of the coat