An 18 year-old man presents to the office for evaluation of multiple swellings in his neck. On examination, he has multiple large lymph nodes in his neck. Neurological examination reveals poor coordination on walking. Biopsy of lymph node is positive for lymphoma. He is diagnosed with ataxia-telangiectasia. What is the etiology of this disorder? A-Defective DNA repair mechanisms B-Deletion of VHL gene on chromosome 3 C-Mutation in the NF1 gene on chromosome 17 D-Mutation in PKD1 on chromosome 16 E-Mutation in APC gene on chromosome 5 Answer