Chromosome changes in methotrexate-resistant cell lines ofDrosophila melanogaster

摘要

Cells resistant to methotrexate (MTX) were obtained from two established cell lines ofD. melanogasterand a karyological analysis was performed. No conspicuous changes in the frequencies of cell types were observed in MTX-resistant (MTXR) subline 0.57, as compared with the original line, whose cells were mostly near-tetraploid. On the contrary, altered karyotypes were frequently noticed in the C1 82 MTXRsubline, as compared with the original line, whose cells were mostly diploid. The C1 82 MTXRsubline was characterized by mostly tetraploid cells and by the presence of chromosome fragments (in 48 of them). The mitotic segregation suggests the presence of a centromere in these fragments and the fluorescence pattern, after quinacrine staining, suggests that they may be derivatives of the X chromosome.