Incomplete dominance can be explained:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → When F1 progeny does not resemble either of the two parent.
In incomplete dominance, neither allele of a pair is fully dominant. The F1 hybrid therefore shows a phenotype in between those of the two parents. In snapdragon, a cross between red (RR) and white (rr) flowers gives pink (Rr) flowers in F1. On selfing, F2 gives 1 red : 2 pink : 1 white. The genotype ratio is the usual 1 : 2 : 1, and the phenotype ratio also becomes 1 : 2 : 1.
(1) When F1 progeny resembles dominant parent. — Incorrect. This is complete dominance, as in Mendel’s tall and dwarf pea plants.
(2) When F1 progeny does not resemble either of the two parent. — Correct. The blended, in-between phenotype is the mark of incomplete dominance.
(3) When F1 progeny shows both dominant and recessive features. — Incorrect. Both traits appearing together, each fully, is co-dominance, as in the AB blood group. In incomplete dominance the traits blend into a new one.
(4) When F2 progeny does not resemble either of the two parent. — Incorrect. The in-between phenotype is seen in the F1, not the F2. The F2 has red and white plants that look like the original parents.
NCERT Extract:
Incomplete Dominance –
