lab5 - 5 Genetics and Cellular Function Objectives In this...

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29 5 Genetics and Cellular Function Objectives In this chapter we will study the characteristics of cancer cells; some methods of cancer detection; several treatments for cancer; how pedigrees represent hereditary patterns in families; and how genetic counselors determine the risk of transmitting genetic diseases. Cancer Cancer is second only to heart disease as a leading cause of death in the United States; approximately one-fourth of the population develop some form of cancer during their lifetimes, and a diagnosis of cancer is one of the most dreaded pronouncements a person can hear. Cancer is not a single disease, but a group of pathologies with certain properties in common (especially the potential for metastasis). The first column of table 5.1 ranks the 10 most common forms of cancer in the United States in 1997 according to incidence, while the second column gives the mortality rates for those types. (To refresh your memory of the terms incidence and mortality , see chapter 1 of this manual.) You can see that different forms of cancer differ greatly in mortality, either because they progress slowly, as in prostate cancer, or because they are highly treatable, as in skin cancer. The top 10 cancers in the United States, from the highest to the lowest mortality rate, are cancer of the lung, colon, breast, prostate, pancreas, blood-forming tissue (leukemias), ovary, stomach, brain and other nervous system, and bladder. Characteristics of Cancer Cells The change from a normal cell to a cancerous cell is called transformation. Cancerous cells lack the structural characteristics and functions of mature, differentiated cells. Cancerous cells of the lung, for example, cannot carry out normal lung functions. Transformed cells exhibit two heritable charac- teristics: anaplasia and autonomy . Anaplasia is the lack of differentiation—that is, a lack of specialized form and function. Anaplastic cells resemble embryonic cells rather than mature cells. It is uncertain whether they result from mature cells reverting to embryonic form or from the multiplication of tissue stem cells that never differentiated in the first place. Autonomy refers to the fact that cancer cells are independent of the normal mechanisms that control the rate of cell division. Cancer cells typically show enlarged nuclei, abnormally dense DNA, and increased mitotic activity. Their rapid mitosis and lack of histological organization enable tumor cells to invade and destroy neighboring tissues. This invasion is called progression. In metastasis, cells from the primary tumor (original site) break loose, travel in the blood or lymph, and invade distant organs, where they seed new tumors. Thus, lung and prostate cancers often metastasize to the brain, while colorectal, prostate, and breast cancers often metastasize to the lungs and liver. Some cancer cells also exhibit the following intracellular and surface changes: 1.
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This note was uploaded on 11/16/2011 for the course SCIENCE Anatomy an taught by Professor Tory during the Spring '11 term at Kennesaw.

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lab5 - 5 Genetics and Cellular Function Objectives In this...

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