In a dihybrid cross between two plants, one with genotype AaBb and the other wit
Practice Questions
Q1
In a dihybrid cross between two plants, one with genotype AaBb and the other with genotype Aabb, what fraction of the offspring will be expected to show the dominant phenotype for both traits?
1/4
1/2
3/4
1/8
Questions & Step-by-Step Solutions
In a dihybrid cross between two plants, one with genotype AaBb and the other with genotype Aabb, what fraction of the offspring will be expected to show the dominant phenotype for both traits?
Step 1: Identify the genotypes of the parent plants. One plant has genotype AaBb and the other has genotype Aabb.
Step 2: Determine the possible gametes (sperm and egg) each parent can produce. The AaBb parent can produce gametes AB, Ab, aB, and ab. The Aabb parent can produce gametes Ab and ab.
Step 3: Set up a Punnett square to combine the gametes from both parents. The rows will represent the gametes from AaBb (AB, Ab, aB, ab) and the columns will represent the gametes from Aabb (Ab, ab).
Step 4: Fill in the Punnett square with the combinations of the gametes. This will give you the offspring genotypes: AABb, AAbb, AaBb, Aabb, aaBb, aabb, etc.
Step 5: Count the total number of offspring genotypes that show the dominant phenotype for both traits (A_ and B_). The dominant phenotypes are AABB, AABb, and AaBb.
Step 6: Calculate the fraction of offspring that show the dominant phenotype for both traits. There are 3 genotypes (AABB, AABb, AaBb) that show the dominant phenotype out of a total of 8 possible combinations.
Step 7: Therefore, the fraction of offspring expected to show the dominant phenotype for both traits is 3 out of 8, or 3/8.
