Ataxia-Telangiectasia: Curse Of The Chromosome

Introduction
    Ataxia-telangiectasia (A-T), also called Louis-Bar syndrome, is a rare genetic disease, classified as an autosomal recessive, complex, multisystem disorder. (Jozwiak 2005) Individuals with A-T rarely survive beyond their early 20s. Nervous system abnormalities become apparent by age two, and muscle control progressively diminishes. Immune system deficiencies and blood cancers are common, and affected individuals are extremely sensitive to radiation. (BookRags 2005).
    History
    A-T first appeared in the medical literature in the mid-1920s, (Syllaba and Henner 1926) but was not named as a specific disorder until 1957. (Sedgwick and Boder 1958). The name is a combination of two recognized disorders: ataxia (lack of muscle control) and telangiectasia (tiny, red spots), however, A-T is more than the sum of these two disorders. Other A-T- associated indicators include immune system deficiencies, extreme sensitivity to radiation, and blood cancers. (Mizutani 2005)
    Medical researchers initially suspected that multiple genes (the units responsible for inherited features) were involved. However, in 1995, mutations in a single large gene were identified as causing A-T. The gene was named ATM (for A-T, mutated) and subsequent research revealed it has a significant role in regulating cell division. ( BookRags 2005) In 1988 this gene was mapped to band 11q22-23. ( Jozwiak 2005). The subsequent identification of the gene proved difficult; it was 7 more years until the human ATM gene was cloned. The diverse symptoms seen in A-T reflect the main role of ATM, which is to induce certain cellular responses to DNA damage. When the ATM gene is mutated, these signaling networks are impaired, and so the cell does not respond correctly to minimize the damage.(NCBI 2005)
    Cause
    Ataxia-telangiectasia (A-T) is one of a group of recessively inherited ataxias and a prominent example of a genomic instability syndrome. A-T is caused by loss of function of...