55549 IMGP3193

Ataxia-teleangiectasia

One basie defect of the malady is the abnormal sensitiyity of A-T cells to x-rays and certain radiomimetie Chemicals but not to ultraviolet irradiation, which leads to chromosom* and chromatid breaks.

Breakpoints are randomly distributed, but nonrandom chromosome rearrangements selectively affcct chromosomes    at sites that are

concerned with T-cell receptors and heavy-chain immunoglobulin coding and with the deveiopment of hematologie malignancies. Such disturbances could account for the frequency of infections and neoplasias.