AS.020.305 Midterm: cell bio final study sheet (dragged) 2
Document Summary
Cease dividing after 25-40 divisions, a process called replicative cell senescence, as we discuss later: mammalian cells occasionally undergo mutations that help them proliferation indefinitely in culture as immortalized cell lines. Although they are not normal, they are widely used for cell cycle studies. Cell*cycle*control*system*triggers*the*major*events*of*the*cell*cycle: sensors, for example, detect the completion of dna synthesis, and if some malfunction prevents the successful completion of this process, signals are sent to the control system to delay progression to m phase. It would clearly be disastrous, for example, if events like chromosome condensation or nuclear envelope breakdown were only partially initiated or started but not completed. Second, the cell-cycle control system is remarkably robust and reliable, partly because backup mechanisms and other features allow the system to operate effectively under a variety of conditions and even if some components fail.
