<prompt> Defect in xeroderma pigmentosum RepeatMismatch repairBase excision repairNucleotide excision repairDouble strand break repair  <response>: Ans: C Nucleotide excision repair Ref: Robbins Pathologic Basis of Disease, 8th edition, Pg: 275 Frosiius G Commentary: DNA base excision repair defects in human pathologies Free Radic Res. 2004 Oct:3810: 1037-54.Explanation:Types of defects in DNA-repair systems and conditions associatedDNA Repair MechanismsDiseases associatedMismatch repair Hereditary Nonpolyposis Colon Cancer Syndrome Muir-Torre SyndromeNucleotide excision repair Xeroderma pigmentosum Cockaynes syndrome T richothiodystrophyBase excision repair Gross defects - Not compatible with life Partial defects -Colorectal cancer LungRecombinational repairCancers Ataxia Telangiectasia ATM gene, genome instability syndrome Bloom syndrome RecQ DNA helicase; BLM gene Fancont anemia BRCA-2 Werner syndrome WRNp protein- RecQ DNA helicaseDirect Repair-- DNA damaging agent X-raysoxygen radicals internalexternal alkylating agents spontaneousUV-light oxygen radicals internalexternalX-raysoxygen radicals internalexternal UV-lightanti-tumor agentsreplicationerrorsnon-enzymatic methylation of DNA by cellular S-adenosyl- methionineLesionsUracilabasic site 8-oxoguanme single-strand break6-4 photoproduct bulky adducts cyclobutane pyrimidine dimerdouble-strandbreakinterstrand-crosslinkA-G mismatchT-C mismatch insertiondeletionO-6-methyl-guanineRepairprocessBase excision repair BERNucleotide excision repair NERRecombinational repair HRNHEJMismatch repair MMRDirect reversal DR 