Abstract |
Since the finding that the L5178Y TK+/- -> TK-/- forward mutational assay system can detect and distinguish a range of mutational events, including large chromosomal aberrations and smaller, perhaps point mutational events, the chromosomal analysis of these lesions at the highest possible level of band resolution has become increasingly important. The TK+/- 3.7.2C cell line contains chromosomes 11 of normal morphology when investigated by high resolution banding techniques. In the mouse, tk-1 has previously been mapped by somatic cell genetics to chromosome 11. The study investigated the sublocalization of the break points in chromosome 11 deletions, translocations, and insertions occurring in induced TK-/- mutants. We developed an acridine orange/Colcemid/hypotonic treatment of TK-/- mutants to provide high resolution chromosomes with over 500 G-bands for break point analysis. Using both standard and high resolution procedures, the study found that independently induced smallcolony mutants show rearrangements in the distal portion of chromosome 11, with break points occurring between bands B5 and D1.3. The finding of a range of chromosomal break points in different TK-/- mutants is consistent with the hypothesis that chromosomal lesions occurring in small-colony mutants may affect a large portion of the genome in the vicinity of the TK gene, and with recent molecular genetic analysis of mutants. (Copyright (c) 1989 Elsevier Science Publishers.) |