Unlock the Secrets of DNA: Rock the 2025 Science Olympiad Heredity Test!

Incomplete dominance is characterized by a scenario where one allele does not completely overshadow the influence of another allele, leading to a blending of traits in the phenotype. This phenomenon occurs when the heterozygous genotype expresses a phenotype that is intermediate between the two homozygous phenotypes.

For example, in plants with flower color, crossing a red-flowered plant with a white-flowered plant may result in offspring with pink flowers. This pink coloration results from the blending of the red and white traits, showcasing that the alleles for flower color do not exhibit complete dominance over each other. Instead of one trait completely masking the other, the physical expression reflects a mix of both.

In contrast to this, complete dominance would involve one allele completely masking the effects of another, and the presence of two dominant alleles would typically signify co-dominance or complete dominance. The option regarding only recessive traits being expressed does not apply here, as incomplete dominance requires at least one dominant allele to mix with a recessive allele for the blending effect to occur. Thus, the essence of incomplete dominance is accurately captured by the blending effect described in the correct answer.