22. If a disorder is completely recessive (tt), what must the normal parents be in order for the child to show the disorder?
The process of thinking is this way. The child's genotype is "tt", so each parent had to donate a single "t". The parents are normal, which means each parent has a dominate "normal" of "T".
So the parents are both "Tt" x "Tt", this means that the probability of being "normal" is 3/4, the probability of having the recessive disorder is 1/4.
