A Mutation that Blocks Initiation of DNA Synthesis in Hamster Cells
The DNA negative mutant of Syrian hamster cells, ts BN-2 stops synthesizing DNA within 2 h of shift to the nonpermissive temperature of 39.5°C. This occurs in exponentially growing cells and synchronized cells put at restrictive temperature at the start of S phase. Although the amount of DNA synthesized is reduced, the fraction of cells in S phase is similar to wild-type BHK-21 cells. DNA fiber autoradiography shows that in the mutant at restrictive temperature the rate of DNA chain elongation is not reduced. Initiation is decreased as shown by an increase in the intervals between active replication origins and a decrease in the relative frequency of initiation events immediately after shift to nonpermissive temperature.
KeywordsMutant Cell Restrictive Temperature Permissive Temperature Nonpermissive Temperature Cell BioI
Unable to display preview. Download preview PDF.