Two heterozygous parents (Aa x Aa) have children with complete dominance. What is the expected phenotypic ratio?
Answer and explanation
Correct answer: D. 3 dominant to 1 recessive
- Step 1: The cross gives genotypes AA, Aa, Aa and aa. Step 2. Three of four show the dominant trait, giving 3 : 1. Answer: 3 dominant to 1 recessive. Why not the others: 1 : 1 is a test cross ratio; 1 : 2 : 1 is the genotype ratio or incomplete dominance; all dominant needs one AA parent.
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