In Antirrhinum (Snapdragon), a red flower was crossed with a white flower and in F1 generation pink flowers were obtained. When pink flowers were selfed, the F2 generation showed white, red and pink flowers. Choose the incorrect statement from the following:
Answer: (D) Law of Segregation does not apply in this experiment. Answer: (D) Law of Segregation does not apply in this experiment Solution: Snapdragon flower colour is a classic case of incomplete dominance: red (RR) x white (rr) gives pink (Rr) F1, and the F2 shows 1 Red : 2 Pink : 1 White.
- A.This experiment does not follow the Principle of Dominance.
- B.Pink colour in F1 is due to incomplete dominance.
- C.Ratio of F2 is 1/4 (Red) : 2/4 (Pink) : 1/4 (White)
- D.Law of Segregation does not apply in this experiment✓
Correct Answer
(D) Law of Segregation does not apply in this experiment
Solution & Explanation
Answer: (D) Law of Segregation does not apply in this experiment Solution: Snapdragon flower colour is a classic case of incomplete dominance: red (RR) x white (rr) gives pink (Rr) F1, and the F2 shows 1 Red : 2 Pink : 1 White. The genotype ratios are exactly as in a normal Mendelian monohybrid cross, so the Law of Segregation DOES apply (alleles still segregate); only the Law of Dominance is not followed because R is not completely dominant over r. Therefore option 4 is the incorrect statement. NCERT Reference: NCERT Class XII, Ch 4, p.60, lines 010-018: "In a cross between true-breeding red-flowered (RR) and true- breeding white-flowered plants (rr), the F1 (Rr) was pink... the F2 resulted in the following ratio 1 (RR) Red: 2 (Rr) Pink: 1 (rr) White. Here the genotype ratios were exactly as we would expect in any mendelian monohybrid cross, but the phenotype ratios had changed from the 3:1 dominant : recessive ratio."