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

What type of mutation perpetuated through carrier reproduction typically does not express characteristics in individuals who do not inherit two copies?

1. Dominant mutations

2. Lethal recessive mutations

3. Conditional mutations

4. Incomplete mutations

The correct answer is: Lethal recessive mutations

The correct answer pertains to lethal recessive mutations, which are characterized by their impact on individuals only when two copies of the mutation are inherited. In this case, a person who carries only one copy of the lethal recessive mutation (is a carrier) does not express the associated traits or characteristics. This is because the presence of a single normal allele can compensate for the faulty one, allowing the individual to maintain regular function without showing symptoms. Lethal recessive mutations can result in severe consequences if both alleles are mutated. Such traits may lead to significant health issues or developmental problems, which could be fatal, particularly if not expressed until later in life or only in the homozygous condition (having two copies of the mutation). Thus, these mutations tend to persist within a population through carrier reproduction, since carriers do not exhibit the negative consequences associated with the homozygous condition. Other types of mutations, such as dominant mutations, lead to observable traits even when only one copy of the mutated gene is present. Conditional mutations depend on specific environmental conditions to express traits, while the term "incomplete mutations" is not widely recognized in genetic terminology as a category. Therefore, lethal recessive mutations uniquely fit the description provided in the question.