You may have heard that cancer is caused by genetic changes in cells. This article will explain how genetic

 changes are related to the development of cancer and why an individual who is born with an alteration in a

gene may be more prone to developing cancer.

 What is Cancer?

Cancer occurs when cells in the body be-come abnormal such that they divide and form more cells without

control or order.

What Are Genes?

Each cell in your body contains a set of 46 chromosomes (23 pairs). Each chromosome consists of

thousands of sections of DNA, which are called genes. There are about 30,000 genes located on our

46 chromosomes. We inherit one copy of each chromosome, and thus one copy of each gene, from each

of our parents. Consequently, we are born with two copies of every gene. Genes contain instructions for

how our bodies function. These instructions influence the color of our hair and eyes, how we process foods,

the shape of our facial features, and our susceptibility to many diseases.

How Are Genes Involved in Cancer?

Certain genes are responsible for deter-mining when cells divide. If such a gene has acquired an alteration

causing it not to work properly, the cell may not be able to control when it divides. If the cell divides too

quickly it may be-come cancerous. For a normal cell to become a cancer cell, several genes must acquire

alterations. These changes accumulate slowly, which means that cancer is a process that develops over a

period of time. Thus, cancer tends to occur more often in older individuals. As an example, consider the

development of colon cancer. Cells that have accumulated a few genetic alterations may grow into a benign

growth called a polyp. If the polyp goes undetected, the polyp may acquire more genetic alterations and

eventually develop into a cancer.

What Causes These Genetic Alterations that Lead to Cancer? We know that some environmental factors,

such as smoking or sunburns, can increase risk for genetic changes that can cause cancer.

What About Individuals Who Have Inherited Genetic Alterations that Increase the Risk Of Cancer? You may

have heard of individuals with a strong family history of cancer who are born with an inherited “susceptibility” to

developing cancer. This means that a person may carry an inherited alteration in a certain type of gene that

controls the growth of cells. Although the development of cancer requires alterations in several genes, a person

 who is born with such an alteration is one step closer to developing cancer than the average person.