A
molecular lesion or
point lesion is damage to the structure of a
biological molecule such as
DNA,
enzymes, or
proteins that results in reduction or absence of normal function or, in rare cases, the gain of a new function. Lesions in
DNA consist of breaks and other changes in the chemical structure of the helix (see
types of DNA lesions) while lesions in proteins consist of both broken bonds and improper
folding of the
amino acid chain.