What term describes a genetic condition in which neither allele is completely dominant over the other?

The term that describes a genetic condition in which neither allele is completely dominant over the other is known as incomplete dominance. In this situation, the heterozygous phenotype is a blend or intermediate expression of the two alleles. For instance, if one allele is associated with red flowers and the other with white flowers, incomplete dominance would result in offspring with pink flowers, demonstrating a mix of both traits instead of one being fully expressed over the other.

This concept is distinct from codominance, where both alleles are fully expressed in the phenotype simultaneously, such as in the case of blood types which can show both A and B antigens. The terms segregation and multiple alleles refer to different genetic principles and do not address the relationship of dominance between alleles in a particular condition. Therefore, incomplete dominance specifically captures the essence of a genetic interaction where neither allele overshadows the other, leading to a unique expression in the phenotype.