What is the expected genotypic ratio from a dihybrid cross?
Practice Questions
Q1
What is the expected genotypic ratio from a dihybrid cross?
1:2:1
3:1
9:3:3:1
1:1:1:1
Questions & Step-by-Step Solutions
What is the expected genotypic ratio from a dihybrid cross?
Correct Answer: 9:3:3:1
Step 1: Understand what a dihybrid cross is. It involves two traits, each with two alleles.
Step 2: Identify the alleles for each trait. For example, let's say Trait 1 has alleles A and a, and Trait 2 has alleles B and b.
Step 3: Create a Punnett square for the dihybrid cross. This will be a 4x4 grid because there are four combinations of alleles from each parent.
Step 4: Fill in the Punnett square with all possible combinations of the alleles from both traits.
Step 5: Count the different genotypes that appear in the Punnett square.
Step 6: Determine the ratio of each genotype. You will find 9 combinations of the dominant traits, 3 combinations of one dominant and one recessive trait, 3 combinations of the other dominant and recessive trait, and 1 combination of both recessive traits.
Step 7: Write the final expected genotypic ratio as 9:3:3:1.
