Final answer:
The situation in which a heterozygous genotype is associated with a phenotype that is more or less intermediate between the phenotypes controlled by the two homozygous phenotypes is incomplete dominance.
Step-by-step explanation:
The situation in which a heterozygous genotype is associated with a phenotype that is intermediate between the phenotypes expressed by the homozygous genotypes is known as incomplete dominance. In incomplete dominance, neither allele is completely dominant over the other. This pattern of inheritance leads to a blending of traits, where the heterozygous individual expresses a phenotype that is neither dominant nor recessive, but rather a mix of both.
For example, in the classic case of flower color in snapdragons, crossing a true-breeding red flower (CRCR) with a true-breeding white flower (CWCW) results in offspring with pink flowers (CRCW). This demonstrates incomplete dominance, as the pink phenotype is an intermediate form of the red and white parental phenotypes. When two pink flowers are crossed, the offspring can have red, pink, or white flowers in a 1:2:1 phenotypic ratio, showing the reemergence of the parental phenotypes along with the intermediate form.