If you do the punnet square, you will notice that there are two outcomes, and that they have a similar proportion, this is only possible if you math a recessive mouse (lets say the recessive allele is white), and a hybrid, that will show the dominant trait (lets say that black is dominant).
If a p53 gene is defective it may cause cell cycle to stop functioning normally. Without this cell cycle check, cells will divide continuosly creating many chromosomal damage.
