Question

In a study of black guinea pigs and white guinea pigs, 100 black animals were crossed with 100 white animals, and each cross was carried to an F2 generation. In 94 of the crosses, all the F1 offspring were black and an F2 ratio of 3 black:1 white was obtained. In the other 6 cases, half of the Fi animals were black and the other half were white. Why? Predict the results of crossing the black and white Fi guinea pigs from the 6 exceptional cases.

Answer 1

Answer:

As the description in the question suggests, the black colour trait was dominant over the whit colour trait. The changes in the 6 other cases were seen because in this case a heterozygous black guinea pig was crossed with a white guinea pig.

           b          b

B        Bb        Bb

b         bb       bb

The results from this cross show that half of the offsprings produced will be black and half will be white.