DNA damage, repair systems and human hypersensitive diseases.

Damage to DNA from carcinogenic agents is one of the early events involved in carcionogenesis. Damage can be mended by excision repair, which is a set of enzymatic pathways by which damaged sites are removed and normal DNA structure restored. Unrepaired damage interferes with DNA replication producing a variety of alterations in chain growth, initiation and termination and sister chromatid exchanges, some of which may result in mutagenesis, transformation and carcinogenesis. Many human diseases exhibit both alterations in excision repair and elevated levels of carcinogenesis.