What is the expected genotypic ratio of a dihybrid cross?

What is the expected genotypic ratio of a dihybrid cross?

• A. 1:1:1:1
• B. 1:2:1
• C. 9:3:3:1
• D. 3:1

Answer: (B)

In a dihybrid cross, two traits are examined simultaneously, typically following Mendelian inheritance patterns. When considering two traits that are each controlled by two alleles, such as AaBb x AaBb, the expected genotypic ratio from this type of cross is 9:3:3:1. The ratio arises from independently assorting the alleles for each trait, resulting in combinations of genotypes. In this case, "9" represents the dominant phenotypes for both traits, "3" represents the dominant phenotype for one trait and the recessive for the other, the next "3" signifies the opposite condition, and "1" illustrates both traits being recessive. This 9:3:3:1 ratio reflects the probabilities of each possible combination of alleles in the offspring when the parents are both heterozygous for both traits. Each trait sorts independently according to Mendel's law of independent assortment, leading to the final phenotypic and corresponding genotypic distribution. Understanding this concept is fundamental to genetics, as it demonstrates how different genes can interact and sort independently during gamete formation.

In a dihybrid cross, two traits are examined simultaneously, typically following Mendelian inheritance patterns. When considering two traits that are each controlled by two alleles, such as AaBb x AaBb, the expected genotypic ratio from this type of cross is 9:3:3:1.

The ratio arises from independently assorting the alleles for each trait, resulting in combinations of genotypes. In this case, "9" represents the dominant phenotypes for both traits, "3" represents the dominant phenotype for one trait and the recessive for the other, the next "3" signifies the opposite condition, and "1" illustrates both traits being recessive.

This 9:3:3:1 ratio reflects the probabilities of each possible combination of alleles in the offspring when the parents are both heterozygous for both traits. Each trait sorts independently according to Mendel's law of independent assortment, leading to the final phenotypic and corresponding genotypic distribution. Understanding this concept is fundamental to genetics, as it demonstrates how different genes can interact and sort independently during gamete formation.