Exam 11: The Cell Cycle

Researchers pulsed rapidly dividing cultured cells for 30 minutes with radioactive thymidine.The cells were then exposed to a solution containing non-radiolabeled thymidine.Cells were analyzed at 2-hour intervals.At the 2-hour time point,no cells appeared to be dividing.Only after 4 hours did some labeled cells appear to be in M phase.This result can be explained in the following way:

Regulatory proteins that serve to prevent a cell from entering the S phase under conditions of DNA damage are also known as _____.

In human and many other eukaryotic species' cells,the nuclear membrane has to disappear in order for what to take place?

Some cells have several nuclei per cell.How could such multinucleated cells be explained?

The mitotic spindle is a microtubular structure that is involved in _____.

How is plant cell cytokinesis different from animal cell cytokinesis?

Nerve cells lose their ability to undergo mitosis.Instead,they are permanently stuck in _____.

Which of the following is not an effect of mitosis-promoting factor (MPF)involved in moving a cell into M phase?

How might spindle microtubules assist in the process of splitting centromeres?

Once researchers understood that chromosomes are moved by the spindle microtubules,the next question they wanted to answer is how the microtubules function to bring about this process.They used fluorescent labels to make the chromosomes and the microtubular structures fluoresce.When anaphase began (centromeres split),they photobleached a section of microtubules.As chromosomes moved toward the poles of the daughter cells,the photobleached sections of the microtubules remained stationary.This result suggests that _____.

Once a cell completes mitosis,molecular division triggers must be turned off.What happens to MPF during mitosis?