Advanced Placement (AP) Biology Practice Exam

How is a "mutant" defined in genetic terms?

1. An individual with normal and common traits

2. An individual with a mutated allele form

3. An individual with a mixed genetic background

4. An individual unaffected by genetic disorders

The correct answer is: An individual with a mutated allele form

A "mutant" in genetic terms refers to an individual that possesses a mutated allele form. This means that the individual carries a version of a gene that has undergone a change or alteration from the typical or wild-type sequence, which can result in different traits or characteristics. Mutations can occur in various ways, such as through substitution, insertion, or deletion of nucleotides in the DNA sequence. The relevance of the mutated allele is significant because it can lead to the expression of traits that differ from the norm—these traits can be advantageous, harmful, or neutral depending on the context and environment. This definition underscores the importance of genetic variation in evolution, as mutants may contribute to the diversity of a population. In contrast, individuals with normal and common traits do not meet this definition, as they possess the typical alleles. A mixed genetic background does not specifically indicate the presence of a mutation, and being unaffected by genetic disorders does not necessarily relate to whether an individual is a mutant. Thus, the definition pinpoints the key concept of genetic alteration that distinguishes mutants from non-mutants.