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Genes, Chromosomes and Cancer Genes

Genes and chromosomes

Our bodies are made up of millions of cells. Within almost every cell are 46 rod-like structures called chromosomes. Chromosomes are the packages of genetic information that make each person unique. There are 23 pairs of chromosomes. One chromosome of each pair comes from each of our parents. Along the chromosomes are thousands of genes, which are made up of DNA.

What Genes and Chromosomes Do

There are approximately 30,000 different genes and each has an important role in the body. Some genes determine how we will look, while others play an important role in how our bodies grow and develop. Genes also play an important role in disease. Inherited conditions such as cystic fibrosis and sickle cell anemia are caused by changes in our genes. Such gene changes are called mutations, and these mutations can be passed down from a parent to a child.

Cancer Genes

Over the past ten years, the location and the role of hundreds of genes have been determined. Through research, we now know that there are some genes that, when mutated, can give a person an increased risk for cancer. These genes are called cancer susceptibility genes or “cancer genes.” Over 100 different cancer genes have been described, and some of these have been shown to cause an increased risk for different types of cancer including breast cancer, ovarian cancer, colon cancer, thyroid cancer and uterine cancer. There are three classes of cancer genes. These are: proto-oncogenes, tumor suppressor genes, and DNA repair genes. Below are some of the known cancer genes and the family syndromes they cause.

Gene Name

Type of Gene



tumor suppressor gene

Cowden syndrome


DNA repair genes

Hereditary Breast/Ovarian Cancer


DNA repair genes

Hereditary Non-Polyposis Colon Cancer syndrome (HNPCC)



Multiple Endocrine Neoplasia type 2a and 2b

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