In classical Mendelian genetics, what is the expected phenotypic ratio in the F2 generation of a monohybrid cross with complete dominance?
Answer and explanation
Correct answer: A. 3 : 1
- Step 1: Crossing heterozygous parents (Aa x Aa) yields 1 AA, 2 Aa, and 1 aa genotypically. Step 2. Because allele A is fully dominant over a, both AA and Aa exhibit the dominant phenotype, producing a 3:1 phenotypic ratio. Answer: 3 : 1. Why not the others: 1:2:1 is the genotypic ratio; 9:3:3:1 is the dihybrid phenotypic ratio; 1:1:1:1 is a dihybrid test cross ratio.
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