Final answer:
Spontaneous mutations can be classified into three categories: substitution, deletion, and insertion mutations.
Step-by-step explanation:
Spontaneous mutations occur without any exposure to environmental agents and can be categorized into three main types: substitution, deletion, and insertion mutations.
Substitution mutations involve the replacement of one nucleotide with another. For example, a cytosine (C) can be replaced by a thymine (T) in the DNA sequence.
Deletion mutations lead to the loss of one or more nucleotides from the DNA sequence. This can cause a shift in the reading frame, resulting in a nonfunctional protein.
Insertion mutations occur when one or more additional nucleotides are inserted into the DNA sequence. This can also cause a shift in the reading frame and affect the function of the protein.