Thinking Scientifically

1. A cell from a newborn human divides 19 times in culture and is then frozen for 10 years. Upon thawing, how many times is the cell likely to divide?

2. Cytochalasin B is a drug that blocks cytokinesis by disrupting the microfilaments in the contractile ring. What effect would this drug have on cell division?

3. How might the observation that more advanced cancer cells have higher telomerase activity be developed into a test that could help physicians treat cancer patients?

4. A researcher removes a tumor from a mouse and breaks it into cells. He injects each cell into a different mouse. Although all of the mice in the experiment are genetically identical and were raised in the same environment, the animals develop cancers that spread at different rates. Some mice die quickly, some linger, and others recover. What do these results indicate about the cells that made up the original tumor?

5. Why can combining a traditional cancer treatment with an angiogenesis inhibitor be more effective than either treatment alone?

Additional Questions and Terms

1. A researcher classifies mouse tissue cells according to their stage in the cell cycle. She finds that 3% of the cells are dividing. Of the cells in interphase, 50% are in the G1 phase, 40% in the S phase, and 10% in the G2 phase. Based on this information, the investigator concludes that, for the cells in this tissue, the G1 phase is of the longest duration, followed by the S phase. The cells spend the least amount of time in G2. What is the basis for this interpretation?

2. When the United States dropped atomic bombs on Japan in World War II, many people were not immediately killed but suffered slow, agonizing deaths from radiation sickness. The sudden, massive doses of radiation affected the cells in their bodies that proliferate at the highest rates. What types of cells and tissues were most affected?

3. How might the ability to grow cancer cells in laboratory culture help in cancer treatment?

4. Why would cancer developing in a stem cell in the basal layer of the skin’s epidermis be potentially more harmful than cancer arising in a specialized cell closer to the skin’s surface?