Wendy Kohlmann, M.S.

Genetics is frequently in the news on television and radio and in magazines and newspapers.Researchers are identifying new genes and learning more about how they work and function. This research can provide many benefits to individuals and families at risk for inherited diseases. However, keeping up with these new developments and understanding what they mean for you can be a bit overwhelming. To help you become more knowledgeable, we present the first article of a 4-part series reviewing genes, their roles in cancer, their inheritance, and genetic testing.

Genes are the set of instructions inside our cells that tell our bodies how to grow and develop. Each of our estimated 50,000 to 80,000 genes is a recipe for a specific protein that our body ne

eds. Our genes are organized into larger structures called chromosomes. Each cell has 46 chromosomes that are organized into pairs. One chromosome in each pair is inherited from our Mom, the other is inherited from our Dad. Because we have two copies of each chromosome, we also have two copies of each gene.

Our genetic material is made up of DNA which is made up of a series of chemicals, called bases, arranged in different sequences. Scientists abbreviate these chemicals as A, T, G, and C. These letters make up the alphabet that spells out the instructions in our genes. Different combinations of A, T, G, and Cs will specify different proteins to be made by different genes.

Sometimes a change, or mutation, in the sequence of the bases in a gene causes the gene to stop functioning properly. Some mutations may be caused by factors in the environment; other mutations happen by chance. The cause of a mutation cannot usually be determined.

A mutation can affect the function of a gene in the same way a misspelling can affect the meaning of a sentence. Here is an example:

GENE: ATTAGCACTG
SENTENCE: It is raining, so please wear your coat.

GENE: ATTATCACTG
SENTENCE: It is raining, so please wear your goat.

In the same way changing letters can cause a sentence to no longer make sense, changes in the sequence of a gene will cause the instruction it encodes to not make sense in our bodies.
About 5-10% of colon cancers are caused by an inherited mutation. One, such condition, if familial adenomatous polyposis (FAP). This is associated with the development of numerous polyps, called adenomas, in the colon. These polyps are benign, but there is a high risk for these adenomas to become malignant. People with FAP may also develop polyps in other parts of the digestive system, such as in the stomach. Hereditary non-polyposis colon cancer (HNPCC) is another genetic condition that is associated with an increased risk for colon cancer. Though HNPCC is not associated with the development of many colon polyps, people who have HNPCC have an increased risk for colon and other cancers including those of the endometrium (lining of the uterus), ovaries, small intestine, upper urinary tract and stomach. Peutz-Jeghers syndrome (PJS) is a condition associated with polyps called hamartomas. These are different from the polyps that occur with FAP. For people with PJS, the hamartomas most commonly develop in the small intestine, and they are less likely to become cancerous, but sometimes they can cause obstructions and other problems in the digestive system. Juvenile polyposis (JP) is another condition associated with the development of polyps at a young age. More details about PJS and JP are included in some of the other articles in this issue of the newsletter.