Question

Assertion: Antirrhinum is a good example to understand incomplete dominance.
Reason: Heterozygotes show characteristics of both the alleles.
A. Both Assertion and Reason and correct and Reason is the correct explanation for Assertion.
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.
C. Assertion is correct but Reason is incorrect.
D. Both Assertion and Reason are incorrect.

Answer 1

Hint: In complete dominance, the effect of one allele in a heterozygous genotype completely masks the effect of the other. The allele that masks the other is said to be dominant to the latter, and the allele that is masked is said to be recessive to the former. Complete dominance, therefore, means that the phenotype of the heterozygote is indistinguishable from that of the dominant homozygote.

Complete step by step answer: Incomplete dominance also called partial dominance or semi-dominance occurs when the phenotype of the heterozygous genotype is distinct from and often intermediate to the phenotype of the homozygous genotypes. For example, the snapdragon flower colour is homozygous for either red or white. When the red homozygous flower is paired with the white homozygous flower, the result yields a pink snapdragon flower. The pink snapdragon is the result of incomplete dominance. When plants of the F1 generation are self-pollinated, the phenotypic and genotypic ratio of the F2 generation will be 1:2:1. Antirrhinum is a typical example of incomplete dominance by the red allele with the anthocyanin pigment. Any cross between red-flowered and white-flowered snapdragons, give an intermediate and heterozygous phenotype with pink flowers, that carries both the dominant and recessive alleles. Several species of Antirrhinum are self-incompatible, meaning that a plant cannot be fertilized by its pollen.
Hence, the correct answer is option C.

Note: A diploid organism is heterozygous at a gene locus when its cells contain two different alleles of a gene. The cell or organism is called a heterozygote specifically when it refers to a specific genotype. A heterozygous genotype can have higher relative fitness than either the homozygous dominant or homozygous recessive genotype – this is called the heterozygote advantage.