Question

RR( Red) Artirrhinum is crossed with the white (WW) one. Offspring RW are pink. This is an example of:

• A. Incomplete dominance
• B. Dominant-­recessive
• C. Supplementary genes
• D. Hybrid

Answer 1

The correct option is A

Incomplete dominance

The correct option is A.

Explanation of correct option:

1. When a red Artirrhinum with RR allele is crossed with a white Artirrhinum with WW allele, the offsprings in the F1 generation have the allele combination- RW, and the colour will be pink.
2. In this case, red colour is a dominant gene but the presence of both red and white genes results in partial expression of these genes.
3. Such an incident is known as incomplete dominance.

Explanation of incorrect options:

Option B:

1. When a dominant trait is crossed with a recessive trait, the dominant trait is expressed over the recessive trait.
2. In the case of Artirrhinum, RR(red) is the dominant allele but while crossed with WW(white) allele it expresses pink colour in place of red colour.
3. The dominant allele is unable to express fully.
4. It is not a dominant-recessive type of gene expression because both genes are dominating each other.

Option C:

1. In supplementary genes, the expression of one particular gene is dependent on the presence of another gene.
2. In the case of Artirrhinum, the occurrence of red colour is not dependent on white colour but they are both expressed simultaneously.

Option D:

1. Hybrid occurs in presence of heterozygous alleles.
2. In this case of Artirrhinum, the allele for red colour and white colour are both homozygous.
3. So, they can't be hybrid.

Final answer: RR( Red) Artirrhinum is crossed with the white (WW) one. Offspring RW is pink. This is an example of incomplete dominance.