Heterochromatin and chromosome aberrations. A comparative study of three mouse cell lines with different karyotype and heterochromatin distribution

摘要

Mitomycin C induced chromosome aberrations in mouse cells differing in chromosome number and karyotype were studied. The material included (1) laboratory mouse (2n = 40), all telocentric chromosomes possessing centromeric heterochromatin, (2) laboratory mouse X tobacco mouse hybrid (2n = 33) with 7 metacentrics and 26 telocentrics, and (3) ascites tumour cells (MSWBS) — (2n = 28—29), with 9 to 10 biarmed chromosomes, with heterochromatin localised to the centromeric regions in all, except two marker chromosomes — one telocentric with 4 intercalary blocks, and one biarmed chromosome with two terminal blocks. Both chromatid intrachanges and interchanges were scored. It was found: (a) In laboratory mouse about 80% of the abberations are localised to the heterochromatic regions; (b) In the tobacco mouse X laboratory mouse hybrid, the exchanges are between two telocentrics or a telocentric and a metacentric, but seldom between two metacentrics; (c) In the MSWBS tumour cells, the centromeric heterochromatin was involved more often in interchanges than the intercalary blocks, without any restriction between two biarmed chromosomes to form exchanges.