POSSIBLE MECHANISMS OF CHROMOSOMAL-ABERRA TIONS .6. MITOTIC DELAY AS A PROTECTIVE PROCESS - ORIGIN OF SPONTANEOUS CHROMOSOME BREAKS

It was proved by the investigation of the bone marrow cells and the cu lture of embrionic fibroblasts of mice, that experimental induction of chromosome breaks having such a distinctive feature as disposition of acentrics outside the equatorial plate at metaphase, results in reduc tion of the mitotic index and the radiation induced structural mutatio ns frequency. Such disposition of acentrics - outside the equatorial p late - is typical for spontaneous chromosome breaks. It was suggested, that the process resulting in spontaneous chromosome breaks is a comp onent of the protective mechanism, which is put into effect through th e mitotic delay.