A dihybrid cross is a cross between two organisms that are heterozygous for two different traits. This means that each parent carries one dominant allele and one recessive allele for each trait. The offspring of a dihybrid cross will inherit one allele from each parent for each trait, and the possible combinations of alleles are:
- Dominant allele for both traits (DDYY)
- Dominant allele for the first trait and recessive allele for the second trait (DdYy)
- Recessive allele for the first trait and dominant allele for the second trait (ddYy)
- Recessive allele for both traits (ddyy)
The phenotypic ratio of a dihybrid cross is 9:3:3:1, which means that there will be:
- 9 offspring with the dominant phenotype for both traits (DDYY or DdYy)
- 3 offspring with the dominant phenotype for the first trait and the recessive phenotype for the second trait (DdYy)
- 3 offspring with the recessive phenotype for the first trait and the dominant phenotype for the second trait (ddYy)
- 1 offspring with the recessive phenotype for both traits (ddyy)
The genotypic ratio of a dihybrid cross is 1:2:2:4:1:2:1:2:1, which shows the different combinations of alleles that the offspring can inherit.
