X-ray and UV-induced chromatid aberrations: evidence for polynemic chromosomes?
Ikushima and Wolff have recently interpreted both their observation of chromatid aberrations in second and third mitoses following X-irradiation and the production of chromatid type chromosomal aberrations by UV light administered during the G1 phase of the cell cycle in terms of a polyneme model of eukaryote chromosome structure. They were led to do so, however, largely because of their X-ray data, which the interpreted as evidence for the induction of sub-chromosomal lesions (by G1 irradiation; sub-chromatid for G2 irradiation) which appear as chromatid type aberrations only in later divisions. We here report data from similar X-ray experiments in which synchronized Chinese hamster tissue culture cells were irradiated in either G1 or G2 and then scored for chromatid aberrations in their first, second and third post-irradiation mitoses. Our results do not show the effect reported by Ikushima and Wolff. We conclude that all of the data available of aberration production is compatible with a simple mononeme model of eukaryote chromosome structure.
D000818:Animals; D001345:Autoradiography; D002460:Cell Line; D002842:Chromatids / Q000528:radiation effects*; D002869:Chromosome Aberrations; D006224:Cricetinae; D004247:DNA / Q000096:biosynthesis*; D008168:Lung; D008938:Mitosis; D011831:Radiation Genetics; D013936:Thymidine / Q000378:metabolism; D014316:Tritium; D014466:Ultraviolet Rays; D014965:X-Rays
D014316:Tritium; D004247:DNA; D013936:Thymidine