What is the expected phenotypic ratio of a dihybrid cross between two heterozygo
Practice Questions
Q1
What is the expected phenotypic ratio of a dihybrid cross between two heterozygous individuals (AaBb x AaBb)?
3:1
9:3:3:1
1:2:1
1:1
Questions & Step-by-Step Solutions
What is the expected phenotypic ratio of a dihybrid cross between two heterozygous individuals (AaBb x AaBb)?
Step 1: Understand what a dihybrid cross is. It involves two traits, each with two alleles.
Step 2: Identify the genotypes of the parents. In this case, both parents are heterozygous for two traits: AaBb.
Step 3: Determine the possible gametes each parent can produce. Parent 1 (AaBb) can produce AB, Ab, aB, and ab. Parent 2 (AaBb) can also produce AB, Ab, aB, and ab.
Step 4: Create a Punnett square with the gametes from both parents. This will help visualize the combinations of alleles.
Step 5: Fill in the Punnett square with the combinations of alleles from the gametes.
Step 6: Count the different phenotypes that result from the combinations in the Punnett square.
Step 7: Determine the ratio of the phenotypes. You will find 9 with both dominant traits, 3 with the first dominant and second recessive, 3 with the first recessive and second dominant, and 1 with both recessive traits.
Step 8: Conclude that the expected phenotypic ratio for a dihybrid cross (AaBb x AaBb) is 9:3:3:1.
