Answer:
2. independent assortment.
Step-by-step explanation:
According to law of independent assortment, any allele of a gene governing one trait may assort with just any other allele of another trait. As a result of which different combinations of phenotypes may arise.
According to the question given:
black fur (B) is dominant over white fur (b)
rough fur (R) is dominant over smooth fur (r)
A cross between BbRr x BbRr will produce 16 off-springs with genotypes mentioned as under:
BBRR = 1 → Black fur, rough fur
BBRr = 2 → Black fur, rough fur
BBrr = 1 → Black fur, smooth fur
BbRR = 2 → Black fur, rough fur
BbRr = 4 → Black fur, rough fur
Bbrr = 2 → Black fur, smooth fur
bbRR = 1 → White fur, rough fur
bbRr = 2 → White fur, rough fur
bbrr = 1 → White fur, smooth fur
It may be noted here that there are 16 progeny with 4 types of phenotypes mentioned as under:
Black fur, rough fur = 9
Black fur, smooth fur = 3
White fur, rough fur = 3
White fur, smooth fur = 1
We are able to get these results just because of so many allelic combinations formed out of the law of independent assortment.
Rest of the options like intermediate inheritance, multiple alleles and codominance do not apply on these results.
Intermediate inheritance is when we get a blended trait that is grey color but no such phenotype was observed.
Multiple allelism is when there is an existence of a third type of phenotype which is entirely different from both the phenotypes which we didn't observe here.
Codominance is when both the alleles show equal impact like if the guinea pigs had a phenotype which had patches of white and black color then it could be codominance. But here we did not observe any such phenotype.