Answer:
a. F1 genotype PpBb
b. F1 phenotype All black offsprings
c. F2 phenotypic ratio: Black 9/16 cream 3/16 albino 4/16
Explanation:
In rats, the allele for pigmentation (P) is dominant to the allele for albinism (p).
The B gene allele for black pigmentation (B) is dominant to the allele for cream pigmentation (b).
cross 1
pure breeding black rat x albino rat homozygous for cream
parent PPBB x ppbb
a. F1 genotype PpBb
b. F1 phenotype All black offsprings
PpBb x PpBb
c. F2 phenotypic ratio: Black 9/16 cream 3/16 albino 4/16
Twins share the same genes, but siblings born at different time does not share the same genes.
They might not have that alarm response to that chemical substance or they could be far enough from it to not be effective