Question

A third grader decided to breed guinea pigs for her school science project. She went to a pet store and bought a male with smooth black fur and a female with rough white fur. She wanted to study the inheritance patterns of these traits. A cross between these two parents resulted in two litters with a total of 15 F1 progeny, all of which were rough and black. Soon, the F1 litters began to produce F2 progeny, and before long the child had 125 F2 guinea pigs. 8 had smooth white coats, 25 had smooth black coats, 23 were rough and white, and 69 were rough and black. Draw the Punnett Square for the cross between the rough black F1s. How are the coat color and texture traits inherited

Answer 1

Answer:

The F₁ generation had all black and rough fur. Thus, black is dominant over white and rough is dominant over smooth.

Let us consider the two genes B and R for fur color and quality of fur respectively.

In gene B, B is the dominant allele which codes for black color and b is a recessive allele which codes for white color (when present in homozygous condition).

Similarly, in gene R, R is a dominant allele which codes for roughness and r being a recessive allele which codes for smooth fur (when present in homozygous condition).

So, the genotype of parents would be rrBB (smooth and black fur) and RRbb(rough and white fur).

The cross would result in the production of offspring all with rough and black fur that is, RrBb.

The selfing of F₁ generation would result in the production of offspring with four types of phenotypes; smooth white coats, smooth black coats, rough and white, and rough and black.

It shows that the alleles for the coat color and texture traits are inherited independently of each other.

The same is explained with the help of Punnett square in the below attachment.