In a dihybrid cross between two heterozygous pea plants (AaBb × AaBb) exhibiting complete dominance and independent assortment, what phenotypic ratio is expected among the progeny?
Answer and explanation
Correct answer: A. 9:3:3:1
- Step 1: Apply Mendel's law of independent assortment to a dihybrid cross.
- Step 2: Crossing two doubly heterozygous individuals ($AaBb \times AaBb$) yields the classic 9:3:3:1 phenotypic distribution (9 dominant-dominant, 3 dominant-recessive, 3 recessive-dominant, 1 recessive-recessive).
Answer
9:3:3:1.
Why not the others: 1:2:1 is the genotypic ratio of a monohybrid cross; 3:1 is a monohybrid phenotypic ratio; 1:1:1:1 is the testcross ratio for a dihybrid ($AaBb \times aabb$).
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