In Antirrhinum (Snapdragon), a red flower was crossed with a white flower and in \( F_1 \) generation all pink flowers were obtained. When pink flowers were self crossed, \( F_2 \) generation showed white, red and pink flowers. Choose the correct statements for this case:
(A) This experiment does not follow the Principle of Dominance.
(B) Pink colour in \( F_1 \) is due to incomplete dominance.
(C) Ratio of \( F_2 \) is 1 (red): 2 (pink): 1 (white).
(D) Law of segregation does not apply in this case.
Choose the correct answer from the options given below.
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → (A), (B) and (C) only
In the dog flower, R is not completely dominant over r. Red (RR) × white (rr) gives pink (Rr) in F1, and selfing the pink gives 1 RR : 2 Rr : 1 rr in F2.
(A) This experiment does not follow the Principle of Dominance. — Correct. Under dominance the F1 would look like one parent. Pink is in between red and white, so dominance does not hold.
(B) Pink colour in \( F_1 \) is due to incomplete dominance. — Correct. The heterozygote shows a phenotype between the two parents.
(C) Ratio of \( F_2 \) is 1 (red): 2 (pink): 1 (white). — Correct. Each genotype has its own colour, so the phenotypic ratio equals the genotypic ratio, 1 : 2 : 1.
(D) Law of segregation does not apply in this case. — Incorrect. The alleles R and r still separate into different gametes; that is why red and white reappear in F2.
NCERT Extract:
Incomplete Dominance –
