AP BIOLOGY

Detailed explanation-1: -The most common nucleotide mutations are substitutions, in which one base is replaced by another. These can be of two types, either transitions or transversions.

Detailed explanation-2: -Base substitutions are the simplest type of gene-level mutation, and they involve the swapping of one nucleotide for another during DNA replication. For example, during replication, a thymine nucleotide might be inserted in place of a guanine nucleotide.

Detailed explanation-3: -Answer and Explanation: The correct answer to this question is B. They always cause a change to an organism’s genotype. Regardless of the cause of the change, a DNA sequence is always altered when it mutates.

Detailed explanation-4: -Mutations can result from errors in DNA replication during cell division, exposure to mutagens or a viral infection. Germline mutations (that occur in eggs and sperm) can be passed on to offspring, while somatic mutations (that occur in body cells) are not passed on.