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 of those features and was sorry to see that the first litter of eight contained only rough black animals. To her disappointment, the second litter from those same parents contained seven rough black animals. Soon the first litter had begun to produce F2 offspring, and they showed a variety of coat types. Before long, the child had 125 F2 guinea pigs. Eight of them had smooth white coats, 25 had smooth black coats, 23 were rough and white, and 69 were rough and black. a. How are the coat color and texture characteristics inherited? What evidence supports your conclusions? b. What phenotypes and proportions of offspring should the girl expect if she mates one of the smooth white F2 females to an F1 male?

Answer 1

To know what happened here you need to start analyzing the male and female guinea pig that this girl brought at the store.

Male with smooth black fur  

Female with rough white fur

So, you have two characteristics: color and style of fur.

Those are the F0, the start of the bread.

The crossing made a litter of eight contained only rough black animals, this told you the dominance of the alleles:

Black (BB) over white (ww) and rough (RR) over smooth (ss).

Parents are BBss x wwRR = BwRs, BwRs,BwRs, and BwRs

So, the F1 or firs offspring will all have the BwRs alleles and the phenotype will be black rough.

When this F1 is crossed, you had a variety of coats and colors.

BwRs x BwRs =BBRR, BwRs, wBsR, wwss

This explains the variety of colors and coats.