Question

What is the phenotypic ratio of a dihybrid cross in the F2 generation?

Hint:

For standard Mendelian genetics: Monohybrid phenotypic ratio is 3:1, Dihybrid phenotypic ratio is 9:3:3:1.

Answer 1

Step 1: Understanding the Concept:
A dihybrid cross is a breeding experiment between two organisms that are identically hybrid for two traits.

Step 2: Detailed Explanation:
According to Mendel's Law of Independent Assortment, the alleles for two different traits assort independently into gametes.
When considering two traits with complete dominance (e.g., seed shape and seed color), crossing two heterozygous individuals (AaBb $\times$ AaBb) produces a specific distribution of observable traits (phenotypes) in the F2 generation.
The resulting phenotypic ratio is:
9 (Dominant for both traits) : 3 (Dominant for first, Recessive for second) : 3 (Recessive for first, Dominant for second) : 1 (Recessive for both traits).

Step 3: Final Answer:
The phenotypic ratio is 9:3:3:1.