Changes In Genetic Information Research Articles

Mutation rates in cells at different ploidy levels.

AbstractFluctuation tests of the Luria‐Delbrück type have been used to examine the frequency of spontaneous variations in cultures of diploid, tetraploid, and octaploid Chinese hamster cells. Resistance to 8‐azaguanine and altered response to thermal shock were chosen as marker systems. Mutation frequencies of approximately 10−6 and 10−5 have been estimated for heat resistance and azaguanine resistance respectively. Rates of mutation for these markers remain constant or decline slightly in cells with increasing numbers of chromosome sets. This trend is not in accordance with expectations based on the assumption of dominant, co‐dominant, or recessive changes at gene or chromosome levels. It is suggested that at least some variations may arise in somatic cells by stable shifts in phenotypic expression rather than by changes in genetic information.