Explain how DNA could be present on a toothbrush.

• A. DNA is not possible on a toothbrush
• B. DNA present in saliva or shed from mouth cells could be on the toothbrush
• C. Only external environmental DNA would be present
• D. DNA would be destroyed during brushing

Answer: (B)

DNA can end up on a toothbrush through everyday contact with the mouth. The mouth continuously releases saliva and sheds cells from the lining of the cheek and gums. When you brush, these substances—containing DNA from the person using the brush—stick to the bristles and the brush head. So a toothbrush can carry the user’s DNA simply because it touches the mouth and collects material from it. This is the most straightforward source: DNA from saliva and shed mouth cells, not only DNA from the environment. Brushing doesn’t automatically erase all DNA; some of it can remain on the toothbrush for a period, especially if the brush is kept moist or stored without thorough cleaning, making it detectable with the right methods.