I keep getting “Monohybrid ratio” questions wrong in Principles of Inheritance & Variation. What's the trap?
confusing the 3:1 phenotype ratio with the 1:2:1 genotype ratio.
The usual trap: confusing the 3:1 phenotype ratio with the 1:2:1 genotype ratio. How to avoid it: 3:1 is what you SEE; 1:2:1 is the underlying genotype. Go back to the definition — a cross of one trait gives a 3:1 phenotype ratio in the F2 generation.
Key point
Monohybrid ratio
Common mistake
confusing the 3:1 phenotype ratio with the 1:2:1 genotype ratio.
Memory tip
3:1 is what you SEE; 1:2:1 is the underlying genotype.
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