<prompt> All are true about chromosomal instability syndrome except-DNA repair defectAutosomal dominant inheritanceIncreased risk of malignancyAssociated immunodeficiency  <response>: Ans. is b i.e., Autosomal dominant inheritanceo Chromosomal instability syndromes are typically transmitted in an autosomal recessive mode of inheritanceChromosome instability syndromeso They are a group of inherited conditions associated with chromosomal instability and breakage. The disorders are characterized by a defect in DNA repair mechanisms or genomic instabilityo Susceptibility to exogenous genotoxic agents such as ultraviolet UV light, oxidative stress, and chemical mutagens, can also lead to a variety of nucleotide modifications and DNA strand breakso Patients with these disorders show increased predisposition to cancer.o Another hallmark of these disorders is immunodeficiency, a phenotype caused by an inability to properly repair DNA strand breaks that occur during development of the immune system,o Important chromosomal syndromes are1 Ataxia telangiectasia2 Ataxia telangiectasia-like disorder3 Bloom syndrome4 Fanconi anaemia5 Nijmegen breakage syndrome6 Xeroderma pigmentosum,7 Cockaynes syndrome 