The only fact that would allow him to know is if either of his maternal grandparents has PKU
Explanation:
The two alleles for a trait are gotten from the two parents. Hence, for someone to have an autosomal trait, one of the alleles must have come from the father and the other from the mother.
For autosomal recessive traits, a carrier or an heterozygous individuals always appear normal. For Peter's mother to be a carrier for PKU, she must have to inherit the allele from either of her parent. <em>The only way for Peter to know if her mother is a carrier is if either of his grandparents is affected for the disorder. That is, either of them have two affected alleles for the trait where it is certain that Peter's mother will inherit one.</em>
Cells from the cheek are a type of epithelial cell, similar to skin. ... They can be seen faintly even at 40x (scanning power), but the most dramatic images are at 400x where the nucleus is clearly visible as a dark spot in the center of the cell.
choice C would be tempting to choose but the the amount of molecules of a compound most of the time only 1 unless stated otherwise. The more obvious answer is that you can find the amount and kind of atoms in the compound.
