Question
Explain the dihybrid cross of Mendel with an example from Guineapig.
Answer
A dihybrid cross is a genetic cross between two individuals that differ in two traits. For example, in guinea pigs, one trait could be coat colour (black or white) and the other trait could be hair length (short or long). To conduct a dihybrid cross, the parents must be pure for each trait.
If a hybrid black-haired guinea pig (Bb) is crossed with a white-haired guinea pig (bb), the Punnett square for the F1 generation would show that all offspring would have black hair (Bb) because black is dominant over white. However, all F1 individuals would be heterozygous (Bb) for the hair colour trait.
To determine the possible genotypes and phenotypes of the F2 generation, a Punnett square can be used. The genotypes of the F2 offspring would be in a ratio of 9:3:3:1, with 9 having black and short hair, 3 having black and long hair, 3 having white and short hair, and 1 having white and long hair. This ratio can be explained by the law of independent assortment, which states that each pair of alleles segregates independently of other pairs of alleles during gamete formation.
