Choose the correct answer from each of the four options given below:
A homozygous pea plant having purple flowers is crossed with a homozygous pea plant bearing white flowers. The phenotypic ratio of the offspring obtained in F2 generation is:
Topic: Monohybrid F2 phenotypic ratio
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Pick an option and check your answer. The full worked answer is below either way.
Answer
(d) 3:1.
This is a MONOHYBRID cross, and the F2 PHENOTYPIC ratio is 3 : 1 — three purple to one white.
The working:
P: PP (purple) × pp (white) → F1: all Pp, all PURPLE
F1 selfed: Pp × Pp → F2: PP, Pp, Pp, pp
Three of those four LOOK purple (PP, Pp, Pp) and one is white (pp).
THE TRAP is option (c), 1:2:1. That is the GENOTYPIC ratio of exactly the same cross — 1 PP : 2 Pp : 1 pp. Both ratios come from one Punnett square, and the question asks specifically for the PHENOTYPIC one.
Read the word before answering: PHENOTYPIC — what they LOOK like — 3 : 1 GENOTYPIC — what alleles they CARRY — 1 : 2 : 1
3:1.