Algonquin College Health Program Assessment (AC-HPAT) Practice Exam

What characterizes incomplete dominance in genetics?

1. One trait completely masks another

2. Both traits are expressed equally

3. Hybrid offspring exhibit a blend of parental traits

4. Traits are combined in a ratio

The correct answer is: Hybrid offspring exhibit a blend of parental traits

Incomplete dominance is characterized by hybrid offspring that exhibit a blend of parental traits. This occurs when neither allele for a trait is completely dominant over the other. Instead of one trait masking the other or both traits being expressed equally, the result is a phenotype that is an intermediate of the two parental traits. For example, if a red flower and a white flower are crossed, the offspring may produce pink flowers, demonstrating how the traits have blended rather than one overtaking the other. In contrast, complete dominance would be reflected in situations where one trait fully masks another, which is not the case in incomplete dominance. The expression of both traits equally suggests co-dominance, rather than incomplete dominance where the traits merge into a new phenotype. Combining traits in a specific ratio pertains to Mendelian genetics and typically applies to complete dominance cases rather than the blending observed in incomplete dominance. Hence, the defining feature of incomplete dominance is the blended phenotype seen in the offspring, making it the correct response.