Oncogenes, Tumor Suppressor Genes, and Cancer

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How do cells know what to do?

Each cell has a control center called a nucleus. The nucleus contains the information that tells the cell what to do and when to grow and divide. This information comes in the form of genes, which are contained in chromosomes. In the nucleus of most human cells (except for sperm and egg cells), there are 23 pairs of chromosomes. Chromosomes are passed from parents to their children. One chromosome of each pair is inherited from the mother, and the other comes from the father. This is why children look like their parents, and why they may have a tendency to develop certain diseases that run in their families.

Within each chromosome, there are many hundreds to thousands of genes. Genes and chromosomes are made up of long strands of a substance called DNA (deoxyribonucleic acid). Each gene is made up of a specific DNA sequence that contains the code (the instructions) for that gene's function. Genes tell the cell what to do. Many genes tell the cell to make a certain protein that has a specific job or function in the body. Other genes help regulate how much protein another gene makes. Each human cell has about 25,000 genes.

A cell uses its genes selectively; that is, it can turn on (or activate) the genes it needs at the right moment and turn off other genes that it doesn't need. Turning on some genes and turning off others is how a cell becomes specialized. That is how a cell becomes a muscle cell and not a bone cell, for example. Some genes stay active all the time to make proteins needed for basic cell functions. Others shut down when their job is finished and start again later if needed.

Genes, as the basic units of heredity, serve 2 major roles in cancers: some are part of the development of cancer and others protect the body from cancer.

Last Medical Review: 12/27/2011
Last Revised: 12/27/2011