What happens if cells carry on dividing uncontrollably

New cells are produced even if the body does not need them. A group of cancerous cells produces a growth called a tumour. Chemicals and other agents that can cause cancer are called carcinogens.

Carcinogens cause cancer by damaging DNA which can cause mutations to occur. A single mutation will not cause cancer — several are required. For this reason, we are more likely to develop cancer as we get older. There are certain genetic factors that increase the likelihood of developing some cancers. Something that increases the likelihood of developing a disease is called a risk factor. There are several risk factors for various types of cancers. Mitosis Chromosomes carry genetic information in a molecule called DNA.

Some of the cells may detach and be carried around the body in the blood or lymph tissue until they lodge in another organ. There they begin to grow and invade the healthy tissues, forming secondary cancers. This is known as metastasis. Non-malignant tumours are less dangerous than cancers, but they can still cause disease and death depending on where they are growing.

Normal cell division and the development of cancer. Some agents increase the likelihood of cancer-causing mutations occurring in dividing cells. They are known as carcinogens. These include a number of chemicals and ionising radiation, including UV light from the sun. We are exposed to carcinogens in different ways during our lifetime.

The longer we live, the more carcinogens we have met and so the higher our risk of developing cancer. If we deliberately chose to raise the number of carcinogens we are exposed to then we increase our risk of developing cancer. Globally millions of people increase their risk of developing cancers of the lungs, throat and mouth everyday through exposure to the carcinogens in tobacco smoke.

Photo credit: EdBrown Licensed under the Public Domain Mark 1. There are many well known carcinogens, from the tar in cigarette smoke and ethanol in alcoholic drinks to UV light from the sun, asbestos dust, X-rays and radon gas. Choose a carcinogen that interests you and investigate both how people are exposed to the carcinogen and how it affects the cells to cause cancer.

See if you can find out the mechanism by which scientists think the carcinogen affects the cell cycle. Write a report on your findings. Mutations and cancer. Common mutations. This control is brought about at a number of checkpoints as described on page 4 The transformation of a normal cell to a cancer cell usually involves a series of gene mutations.

Cellular Senescence Most cells also seem to have a pre-programmed limit to the number of times that they can divide. Interestingly, the limit seems to be based, in part, on the cell's ability to maintain the integrity of its DNA.

An enzyme , telomerase , is responsible for upkeep of the ends of the chromosomes. In adults, most of our cells don't utilize telomerase so they eventually die. In cancer cells, telomerase is often active and allows the cells to continue to divide indefinitely. For more information on telomerase, see the Cancer Genes section. Continued cell division leads to the formation of tumors.

The genetic instability that results from aberrant division contributes to the drug resistance seen in many cancers. Mutations in specific genes can alter the behavior of cells in a manner that leads to increased tumor growth or development.

Providing reliable information about cancer biology and treatment. Cell Division During a lifetime, many of the cells that make up the body age and die. Reasons that cells are lost and must be replaced include the following: Sloughing off of epithelial cells such as those lining the skin and intestines. The old, worn out cells on the surface of the tissues are constantly replaced.

A special case of this is the monthly replacement of the cells lining the uterus in pre-menopausal women. Wound healing requires that cells in the area of the damage multiply to replace those lost.

Viral diseases such as hepatitis may also cause damage to organs that then need to replace lost cells. Replacement of the cells that make up blood. Red blood cells carry oxygen to tissues. White blood cells such as B and T lymphocytes are part of the body's immune system and help to ward off infections. Most of these cells have very short lifespans and must be constantly replaced.

The precursors of these cells are located in bone marrow. These precursors, or stem cells, must reproduce at a very high rate to maintain adequate amounts of the blood cells.