Cancerous tumors are characterized by abnormal cell division. Normal cells only divide when presented with an external stimulus and they stop dividing when they come into contact with like cells. Cancer cells do not exhibit contact inhibition and they bypass the normal checkpoints in the cell cycle that control and limit cell division. The ability of chemotherapy to kill cancer cells depends on its ability to halt cell division. Usually, cancer drugs work by damaging the RNA or DNA that tells the cell how to copy itself in division. If cancer cells are unable to divide, they die. The faster that cancer cells divide, the more likely it is that chemotherapy will kill the cells, causing the tumor to shrink. Unfortunately, chemotherapy does not know the difference between cancer cells and normal cells. When chemotherapy affects normal cells, side effects such as hair loss, mouth sores, low blood counts, and nausea can occur. Which statement provides the most accurate description of why these side effects are most commonly associated with chemotherapy? A) These side effects are found at the site of the most common form of cancer: GI tract, blood, and skin. B) Chemotherapy targets fast growing cells, including cancer cells, skin cells, GI cells, and blood cells. C) The chemotherapy kills off the smallest, weakest cells including cancer, GI cells, blood cells, and skin cells. D) Side effects are most likely to occur in areas exposed to the outside environment including: GI tract, blood, and skin.
