Zum Inaktivierungskriterium Für Einzelzellen unter Besonderer Berücksichtigung der Teilungsfähigkeit Röntgen- und UV-bestrahlter Saccharomyces-Zellen Verschiedenen Ploidiegrades

Abstract

The ability of UV-and X-irradiated haploid, diploid and tetraploid cells of Saccharomvces to divide was investigated by making pedigrees with a micromanipulator. After irradiation 4 types of cells were observed, 1. cells which never divide, 2. those which divide but do not grow to form visible colonies, 3. cells growing up to visible colonies, which have descendants unable to form a visible colony, and 4. cells which have only descendants forming visible colonies. Quantitative investigations show that the frequency of type 3 cells is high compared with type 4 cells, although type 3 and 4 cells are normally counted as "survivors". This result indicates that "survivors" are not necessarily free of radiation damage causing lethality. The mechanism is discussed, which gives rise to unviable descendants from "surviving" Saccharomvces ceils. A new type of curve is proposed, called "curve of lethality", which looks rather better for characterizing radiation-induced lethal damage than the usual inactivation curves.