Number 1:4
number 2: 3
number 3: 1
Answer:
1/2
Explanation:
Let's assume that the allele "p" is responsible for PKU in the homozygous state. According to the given information, both the parents are unaffected by the disorder but have an affected child. This means that both the parents carry at least one copy of the recessive allele responsible for the disease. Therefore, the genotype of each of the parents is Pp. A cross between Pp and Pp would produce progeny in following ratio=
Pp x Pp = 1/4 PP: 1/2/ Pp: 1/4 pp
Therefore, the probability that their next child will carry just one recessive allele is 1/2.
There is much more fresh water underground than on the surface. A rock layer must be porous and permeable to be a good aquifer. An impermeable layer makes up the bottom of an aquifer. The water table rises and falls with additions or subtractions to the groundwater system.
I believe the answer is B.