a pup will have white short fur, with the odds of 1 in 16 or 6.25%
For this problem, I will use the following notation.
c = Recessive for white fur.
C = Dominant for brown fur.
l = Recessive for short fur.
L = Dominant for brown fur.
Both parent mice have the genes cClL, so their respective eggs and sperm can be one of 4 different set of genes. They are cl, cL, Cl, CL.
For a pup to have white, short fur, it has to have the genes ccll. Any other combination will result in either brown fur, or long fur, or both. That in turn means that both the egg and sperm that went into making the pup have to have the genes cl. No other combination will do.
Since the change of getting a cell with only cl is one of the four possible choices, there's a 1 in 4 chance of the proper type of egg or sperm cell to be used. And since you have both a mother and a father, you have a 1/4 chance for both. So you multiply them together. So the probability of a pup having white short fur is 1/4 * 1/4 = 1/16 = 0.0625 = 6.25% = 1 in 16.
