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39. What is incomplete dominance? Explain it with reference to flower colour in Snapdragon.


It’s a phenomenon in which the F1 hybrid exhibits intermediate characters of the parental gene.

  1. It is seen in flower colours of Mirabilis jalapa (4 O'clock plant and Antirrhinum majus (Snapdragon).

  2. 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 Red (RR) : 2 Pink (Rr) : 1 White (rr). Here the phenotypic ratio deviates from the Mendel's monohybrid cross.

  3. Both phenotypic and genotypic ratio will be the same 1:2:1.

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