Question

With reference to flower colour in snapdragon, explain incomplete dominance.

Answer 1

Hint: Antirrhium is the generic name of the snapdragon. The Snapdragon flower is also called the dragon flower because of its resemblance to the face of a dragon.

Complete Answer:
Incomplete dominance: Incomplete dominance is also called partial dominance or semi-dominance.
- In incomplete dominance, both the alleles in heterozygous condition partially express themselves. Here the dominant allele can not completely mask the effect of recessive allele.
- The physical appearance of the organism shows the blending of both the two alleles i.e. dominant allele as well as recessive allele.

Example of incomplete dominance:
- Cross pollination between red snapdragon and white snapdragon result in pink snapdragon.
 Here, neither the white allele or red allele is dominant.
- The pink colour results from the blending of both the two alleles that are white allele or white and red allele.
- RR represents the dominant red allele and rr represents the recessive allele.
- In F1 ( filial 1 ) generation, all the offspring will be of pink colour having genotype Rr.
- And in F2 generation when two heterozygotes are crossed and results in 1 red coloured snapdragon, 2 pink coloured snapdragon and 1 white coloured snapdragon in the ratio 1:2:1.

Note: Incomplete dominance does not follow the Mendel’s dominance law which states that the dominant character will completely mask the effect of the recessive character.