Chromosomal evolution in the Ehrlich‐Lettré complex of hyperdiploid mouse ascites tumors: Results from seven laboratory strains

摘要

The chromosomes of 7 strains of the hyperdiploid Ehrlich-Lettré mouse ascites tumor (ELD) were analyzed by conventional stainings and by G- and C-bandings. A tendency to slow decrease in chromosome number during a 20-year period was revealed in the 7 strains and in the ELD complex in general. A G-band idiogram of the normal mouse chromosomes was elaborated with numbering of regions and bands. By G-band analysis the following average composition of the ELD karyotypes was indicated: unchanged mouse chromosomes (30%,), marA, marB, minutes (11%), mar1—mar12, telocentric markers (10%), anonymous telocentric markers, often strongly rearranged (50%). Great differences were revealed among normal chromosomes and markers in their capacity to persist in the tumor stemline as structurally stable units. The presence of some unchanged chromosomes in most cells of all 7 strains indicated that they involved selective advantage. Evidently chromosomal evolution has operated by preferably maintaining certain elements unchanged and by submitting other elements to heavy rearrangement. The C-band analysis showed that, in addition to the centromeric C-heterochromatin present in all chromosomes, some had interstitial C-bands, as marA in all strains, mar5 and mar7 in specific single strains, and others in numbers varying among the strains.