A. MOLECULAR REPAIR DNA Repair (DIRECT REPAIR) 1 Certain covalent DNA modifications are directly reversed by enzymes such as __, which CLEAVES ADJACENT PYRIMIDINES DIMERIZED BY UV LIGHT. This chromophore-equipped enzyme FUNCTIONS ONLY in LIGHTEXPOSED CELLS. 2 Minor adducts, such as methyl groups, attached to the O6 position of guanine are removed by __