Question

Consider the three graphs below, which show the quantity of DNA in cells measured by fluorescence in flow cytometry. The x-axis represents the relative amount of DNA per cell, and the relative intensity of the florescence on the y-axis represents the number of cells with that amount of DNA in the cell. Look at the experiment shown on page 248 of your textbook. 1) A B C 2) 20-40,一60一助100 20-40 60一負100 40, 60 N 100 Amount of fluorescence per cell (fluorescence) f fluorescence per cell (luorescence) In the experiments described below, human cells are grown in culture. This means that cells are grown in a test tube, not in arn organism. To record data, the cells are collected, and a fluorescent dye is added to the cells, the dye binds specifically to DNA. The flow cytometer can separate individual cells and measure the amount of fluorescence in each cell. High levels of fluorescence indicate a greater amount of DNA in individual cells. Cells with less DNA are to the left on the graph, while cells with the most DNA are to the right in these graphs. To interpret the graphs, you need to understand what part of the cell cycle each peak in the graph represents. The G1 phase is a period of cell growth, immediately after mitosis and cytokinesis. The S phase is when the cell synthesizes DNA in preparation for mitosis. The G2 phase is a second growth period, in which the cell finishes preparing for mitosis

Answer 1

1. The A region represents G1 phase of cell cycle. All its cells have less amount of DNA.

B region represents S phase and C region represents G2 phase of cell cycle. The amount of DNA in cells of G2 is/should be double than the cells of G1. This is being shown in the first graph.

2. and 3. Compound X inhibits S phase. So, Graph 2 represents it. It is showing the peak of G1 phase only. S phase peak is not there. This means that the S phase has been inhibited.

Graph 3 represents Compound Y. It is showing the G1, S and G2 phases but the peak for M phase is missing.

4. Yes, any compound that inhibits cell cycle can be used as a drug to treat cancer. Cancer is unlimited proliferation of cells and inhibiting the interphase will inhibit the unlimited proliferation of cells.