7.06 Spring 2007 PROBLEM SET 2 Question 1. You are studying the cell division cycle of a mammalian cell line grown in culture. Your goal is to determine how long cells spend in each part of the cell cycle. The culture is not synchronized: each cell in the culture is going through a cell cycle independent of the other cells. Therefore, at any point in time, a range of cell cycle states is present. You pulse the cells for 30 minutes with BrdU, wash it out, and then add an excess of cold thymidine (in what is called a pulse-chase experiment). Following the Pulse-Chase treatment, you remove an aliquot of cells every hour and perform the following types of analysis. Analysis 1: First you count the number of cells in each aliquot and calculate the total number cells in the culture flask at various times. Your results are shown in figure 1. Analysis 2: Next, you stain the cells with fluorescent anti-tubulin antibodies and (using a microscope) determine the percentage of cells that are undergoing mitosis. At each time point, you consistently find that approximately 5% of the cells are undergoing mitosis.
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