Xeroderma pigmentosum is caused due to abnormalities in:

Ans. B. Nucleotide excision repaira. It is transmitted as autosomal recessive and DNA repair mechanism is defective. DNA damage is produced by UV irradiation especially thymine dimers, cannot be incised. Inborn deficiency of the enzyme "nicking endonuclease" is there.b. Clinical manifestations: produces blisters on the skin.c. Dry keratosis, hyperpigmentation and atrophy of skin.d. May produce corneal ulcers.