Incomplete Dominance - Snapdragon , Dog flower

 

INCOMPLETE DOMINANCE 

Incomplete dominance is a genetic phenomenon in which - 

When two genes are present together then both alleles of this gene are expressed incompletely or partially. As a result  the hybrid or offspring or progeny exhibit the intermediate characters of both the parents. 

On the other hand, In incomplete dominance, the dominant allele is not able to conceal the effect of the recessive allele completely.

In this phenomenon, Offspring or progeny do not resemble the parent in terms of character. Offspring assumes the transition state of characters between the parents. This phenomenon deviates from the phenotypic ratio of Mendal law of dominance.

Incomplete dominance occurs because neither of the two alleles is completely dominant over the other. This results in a phenotype that is a combination of both.

After the rediscovery of Mendal law, It came to existence that in most plants, the ratio of Mendel's law of dominance does not exist in both first and second filial generation.

👌👌Remember - Incomplete dominance is seen in the Snapdragon flower or Antirrhinum or Dog flower. It is also found in Four o clock plant or Mirabilas jilapa.

Example of Incomplete Dominance

When a Monohybrid  cross was done between the red and white coloured flowers of the Snapdragon plant. The  allele of the red flower was RR and that for the white flower is rr.

After crossing between the  true-breeding red (RR) and white (rr) coloured flowers of Snapdragon, the F1­ generation produces a pink coloured flower with the allele of  Rr. Afterwards  the allele Rr of F1  progeny was self-pollinated. The flowers were produced -  red (RR), pink (Rr) and white (rr) flowers in the ratio of 1:2:1.This cross indicates that the genotypic and phenotyoic ratio were similar. 

In addition to this, the genotype ratio of F2 generation in the monohybrid cross by Mendel also gave the same ratio of 1:2:1. However, the phenotype ratio has changed from 3:1 to 1:2:1.