Defective DNA repair is seen in -

Ans. is 'b' i.e., Ataxia telangiectasiaAtaxia telangiectasiao Ataxia Telangiectasia (AT) is an autosomal recessive disorder. It is due to mutation of AT gene located on chromosome 11. There is defective DNA repair that results in multiple chromosomal breakso Patients present in first decase of life. Features are : -i) Oculocutaneous telengiectasiaii) Neurological - Ataxia, dysarthria, extensor plantar response, myoclonic jerks, areflexia, distal sensory deficity.iii) Immunodeficeincy-Thymichypoplasiawithcellularandhumoral (IgAandIgG2) immunodeficeincy.iv) Recurrent pulmonary infectionsv) Endocrine disorders- Tye I DMvi) Premature agingvii) Malignancies ? Lymphoma, Hodgkin's disease, acute T cell leukemia, breast cancer.