Final answer:
Uracil glycosylase recognizes and removes uracil from DNA, where it is aberrantly present, either due to deamination of cytosine or incorporation errors during DNA replication, and initiates base excision repair.
Step-by-step explanation:
Uracil glycosylase is an enzyme that plays a critical role in DNA repair processes. This enzyme specifically recognizes and excises uracil from DNA molecules. Uracil is a nitrogenous base normally found in RNA, but when present in DNA, it can arise due to cytosine deamination or through misincorporation during DNA replication. The presence of uracil in DNA can lead to mutations, as it pairs with adenine instead of guanine, thereby inducing a C:G to T:A transition mutation upon replication. Uracil glycosylase recognizes such inappropriate uracil residues in DNA and initiates base excision repair by cleaving the N-glycosidic bond between the uracil base and the deoxyribose sugar, leaving an abasic site, which is further processed by other enzymes in the repair pathway.