Question

In a cross of AACC x aacc, what would be the genotypic and phenotypic ratios of the F2 offspring?

1) 9:3:3:1
2) 1:1:1:1
3) 9:3:4
4) cannot be determined

Answer 1

The F2 offspring from a cross of AACC with aacc will yield a genotypic ratio of 1:2:2:4:1:2:1:2:1 and a phenotypic ratio of 9:3:3:1, according to Mendelian genetics and the principle of independent assortment.

Step-by-step explanation:

The genotypic and phenotypic ratios of the F2 offspring from a cross of AACC (homozygous dominant) times aacc (homozygous recessive) can be determined using principles of Mendelian genetics. When crossing AACC with aacc, all F1 offspring will be AaCc, showing a 1:1:1:1 genotypic ratio. Each F1 plant has the genotype of AaCc because they inherit one dominant and one recessive allele from each parent for both genes.

For the F2 generation, we can reference a dihybrid cross, which typically yields a 9:3:3:1 phenotypic ratio for two heterozygous parents, AaBb × AaBb. However, the genotypic ratio for our F1 cross (AaCc × AaCc) will yield different combinations of the two genes. Considering Mendel's principle of independent assortment, we can determine the genotypic ratio. Mendelian inheritance suggests the genotypic ratio of a dihybrid cross will be 1:2:2:4:1:2:1:2:1. In terms of phenotypes, due to the dominance of the A and C alleles, a 9:3:3:1 ratio is anticipated, where 9 represents the dominant phenotype for both traits, 3 represents the dominant phenotype for one trait and recessive for the other, and 1 is the recessive phenotype for both traits.