A culture of asynchronously growing fibroblasts was analyzed for cell cycle para
ID: 48669 • Letter: A
Question
A culture of asynchronously growing fibroblasts was analyzed for cell cycle parameters. It was determined that the doubling time of the cells is 44 hours, and the times are 2 hours for M, 18 h for G2, 10 h for S.
What proportion of the cells are in M phase?
The cells are fed radioactive thymine for a short period of time (10 min). What proportion of cells incorporate the radioactive thymine as detectable by autoradiography?
After the short pulse the radioactive thymine is removed from the culture. How much time will elapse before radioactive chromosome in M are detected?
What proportion of cells are in G1?
Explanation / Answer
doubling time=44h. cell cycle runns in G1,S and M. 18h,10h,2h. the portion of cells in M phase will need to know at which point the abservation is made. after initian 28h only the cells will enter in M phase.100% of cells may enter in M phase.
10 min means cells are in G1. nearly 1/(44+1)^2 =51% of the cells will be visualized with thyamine.
as the thyamine is removed, it mght not be ever visible as radioactive chromosome in M phase
most cells will be in G1