Excinuclease

Excision endonuclease also known as "excinuclease" is the nuclease (enzyme) which performs the excision (cut) for nucleotide exchange in DNA repair. This particular enzyme is part of a mechanism that can repair in the G1 phase of the eukaryotic cell cycle specific damages to the DNA in such as thymine dimers caused by UV rays by a mechanism called "nucleotide excision repair" mechanism along with DNA polymerase and DNA ligase enzymes.Its deficiency occurs in a rare autosomal recessive disease called xeroderma pigmentosum, thus diagnosis of this disease is done by measuring the enzyme's level in white blood cells in a blood sample beside the clinical picture of the disease that includes :- "extreme UV sensitivity, Excessive freckling, multiple skin cancers and corneal ulcerations", usually those symptoms occurs during the child's first sun exposure.