ON THE FREQUENCY OF CHROMOSOME EXCHANGES IN A CONTROL POPULATION MEASURED BY CHROMOSOME PAINTING

Chromosome painting has been shown to be a valid and rapid method for quantifying structural chromosome rearrangements in human lymphocytes. The method is particularly useful for detecting stable aberrations wh ich are difficult and expensive to quantify with classical methods. Th e inherent stability of translocations has enabled them to be used as a biodosimeter for chronic and temporally displaced exposure to radiat ion. Translocations may also be useful for quantifying chronic exposur e to other environmental agents which may result in an accumulation of cytogenetic damage with age. Most exposures are chronic and occur at low rates, and conventional cytogenetic methods such as dicentric anal ysis are not expected to be informative. To understand the extent to w hich age and lifestyle factors impact the frequency of stable aberrati ons, we have performed chromosome painting on metaphase-arrested lymph ocytes cultured from 47 healthy adults ranging in age from 19 to 77 ye ars, and from umbilical cord blood obtained from eight healthy full-te rm infants. All subjects had previously been screened to eliminate tho se who had received significant occupational or accidental exposure to radiation or chemicals, and none had received chemo- or radiotherapy. Due to the infrequent occurrence of stable aberrations in peripheral lymphocytes, we analyzed the equivalent of more than 1100 metaphase ce lls from each of these 55 people. An average of one cell in 130 (0.77% ) was observed to have a translocation or a stable insertion. A signif icant relationship between stable aberrations and the square of the ag e is apparent (R(2) = 0.69, Y = 0.0615 + 0.000304 age(2); p < 0.00001) . These results support the hypothesis that stable aberrations accumul ate with time, and are likely to integrate adverse environmental expos ure.