What is an example of spontaneous mutation?

An example of a spontaneous mutation is a base substitution that occurs during DNA replication when a DNA polymerase incorporates an incorrect nucleotide into the growing DNA strand. For instance, if an adenine (A) is mistakenly paired with cytosine (C) instead of thymine (T), this can lead to a point mutation. Over time, if this mutation is not repaired, it can be passed on to subsequent generations during cell division. Spontaneous mutations can contribute to genetic diversity but may also lead to diseases if they disrupt important genes.