Question

Incomplete dominance is shown by
A) Lily
B) Mirabilis
C) Helianthus
D) China rose

Answer 1

Hint: Incomplete dominance is the process in which two - breeding parents are crossed to form an intermediate offspring. In this kind of dominance, the variants are not expressed as dominant or recessive rather the dominant is expressed in a reduced ratio.

Complete answer:
Dominance- It is the phenomenon in which one variant of a gene is present on the chromosome masking the effect of the variant gene that is present on the copy of the chromosome. There are two types of dominance, first is incomplete dominance in which a gene variant has a partial effect as compared to when it is present on both chromosomes and the other is codominance in which different variants on each chromosome both show their traits.

Incomplete Dominance - it is the phenomenon where none of the two contrasting genes or factors is dominant. The expression of the character in a hybrid or f1 individual is intermediate or a fine mixture of the expression of the two factors. The incompleteness is also called mosaic inheritance. In this, we cannot consider it as an example of the pre-mendelian concept of blending inheritance because the parental types reappear in the f2 generation.

There are two flowers, Mirabilis jalapa and Antirrhinum majus. There are two types of flowers in pure red and white colour. When the two types of plants are crossed, the hybrid or plants of the f1 generation have pink flowers. If we self- cross their fi generation, the plants of f2 generation are of three types-red, pink and white flower in the ratio of 1:2:1. The pink colour apparently appears either due to the mixing of red and white colours or the expression of a single gene for a pigmented flower that produced only pink colour.

Therefore the correct answer is option ‘B’.

Note: Codominance is a type of dominance in which both the alleles present on a gene are expressed in the phenotype. It is the result of the relationship between the two versions of a gene of the species. This results in offspring with a phenotype that will neither be dominant nor be recessive. All the traits that are associated with each allele are displayed simultaneously.