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
The inheritance of flower colour in the dog flower (snapdragon or Antirrhinum sp.) is a good example to understand incomplete dominance. In a cross between true-breeding red-flowered (RR) and true- breeding white-flowered plants (rr), the F1 (Rr) was pink. When the F1 was self-pollinated 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. What happened was that R was not completely dominant over r and this made it possible to distinguish Rr as pink from RR (red) and rr (white).