Chromosome patterns (G and C bands) of in vitro chemical carcinogen-transformed guinea pig cells

The chromosomes of five chemical carcinogen-transformed strain 2 guinea pig fetal cell lines were identified by G and C banding techniques and were compared with the normal karyotype from secondary untreated cultures. One line transformed by benzo(a)pyrene had a diploid constitution with no G and C band alterations. Three lines were near diploid, one was near tetraploid, and each contained abnormal chromosomes. A 3-methylcholanthrene line had an abnormal metacentric chromosome formed by centric fusion of two nonhomologous autosomes. The three N-methyl-N'-nitrosoguanidine or diethylnitrosamine cell lines exhibited submetacentric or subtelocentric abnormal chromosomes originating from translocations between two No. 1 or a No. 1 and another autosome. The involvement of Chromosome 1 may be due to its association with nucleolar organization. The greater frequency of contact between such chromosomes, compared to other autosomes, creates an increased risk of chromatid exchange possibly explaining their frequent participation in abnormal chromosome formation or nondisjunction.