This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Etiological Factors of Neoplasia, Subject name: Pathology
The following have defect in DNA repair mechanism except for: 
Select and explain. 
A. Xeroderma Pigmentosa, B. Fanconi anemia, C. Huntington's disease, D. Ataxia-telangectasia
C: Huntington's disease
Answer: C: Huntington's disease 
Explanation: Huntington disease (HD) Autosomal dominant disease It is a prototypes of the polyglutamine trinucleotide repeat expansion diseases. The gene for it is located on chromosome 4p16.3, encodes a 348 kD protein known as huntingtin. Xeroderma Pigmentosum Inherited disorder of DNA repair Diseases with Defects in DNA Repair by Homologous Recombination: Bloom syndrome Ataxia-telangiectasia Fanconi anemia