Question

pink colored flowers are obtained from a cross between a red flowered snapdragon and a white flowered snapdragon. the appearance of the pink colored flower is known as:
a codominance
b complete dominance
c incomplete dominance
d polygenic trait

Explanation:

• Codominance: Both alleles are expressed simultaneously, like in blood type AB where both A and B antigens are present. But here, it's not a case of both red and white being shown distinctly.
• Complete dominance: One allele completely masks the other. For example, in pea plants, if \(T\) (tall) is dominant over \(t\) (short), \(Tt\) is tall. But in snapdragon flower color, there is an intermediate phenotype.
• Incomplete dominance: The heterozygous phenotype is an intermediate between the two homozygous phenotypes. When a red - flowered (\(RR\)) and white - flowered (\(rr\)) snapdragon are crossed (\(RR\times rr\)), the \(Rr\) offspring show a pink color (intermediate between red and white).
• Polygenic trait: Traits controlled by multiple genes. Flower color in snapdragon in this case is controlled by a single gene pair (assuming simple cross as described), not multiple genes.

Answer:

C. incomplete dominance