Final answer:
The most common type of chemical change that occurs naturally in DNA is deamination. Deamination is the hydrolytic removal of amino (-NH2) groups from guanine, cytosine, or adenine and can lead to base substitutions in the DNA sequence.
Step-by-step explanation:
The most common type of chemical change that occurs naturally in DNA is deamination.
Deamination is the hydrolytic removal of amino (-NH2) groups from guanine, cytosine, or adenine. It results in a purine to purine or pyrimidine to pyrimidine change in the DNA sequence. The removal of adenine or guanine from the DNA through deamination can lead to the formation of unnatural bases (hypoxanthine and xanthine), which can be recognized and corrected by DNA repair systems.
Examples of DNA damage caused by chemical mutagens include the deamination of cytosine by nitrous acid, resulting in its conversion to uracil, and the deamination of adenine to hypoxanthine.