Genetic and cellular function.

Cancer.

Cancer is the uncontrolled growth of abnormal cells in the body. Cancerous cells are also called malignant cells.

Causes.

Cells are the building blocks of living things.

Cancer grows out of normal cells in the body. Normal cells multiply when the body needs them, and die when the body doesn't need them. Cancer appears to occur when the growth of cells in the body is out of control and cells divide too quickly. It can also occur when cells forget how to die.

There are many different kinds of cancers. Cancer can develop in almost any organ or tissue, such as the lung, colon, breast, skin, bones, or nerve tissue.

There are many causes of cancers, including:

• Benzene and other chemicals
• Drinking excess alcohol
• Environmental toxins, such as certain poisonous mushrooms and a type of poison that can grow on peanut plants (aflatoxins)
• Excessive sunlight exposure
• Genetic problems
• Obesity
• Radiation
• Viruses

However, the cause of many cancers remains unknown.

The most common cause of cancer-related death is lung cancer.

The three most common cancers in men in the United States are:

• Prostate cancer
• Lung cancer
• Colon cancer

In women in the United States, the three most common cancers are:

• Breast cancer
• Colon cancer
• Lung cancer

Some cancers are more common in certain parts of the world. For example, in Japan, there are many cases of stomach cancer, but in the United States, this type of cancer is pretty rare. Differences in diet may play a role.

Some other types of cancers include:

• Brain cancer
• Cervical cancer
• Hodgkin's lymphoma
• Kidney cancer
• Leukemia
• Liver cancer
• Non-Hodgkin's lymphoma
• Ovarian cancer
• Skin cancer
• Testicular cancer
• Thyroid cancer
• Uterine cancer

Symptoms.

Symptoms of cancer depend on the type and location of the cancer. For example, lung cancer can cause coughing, shortness of breath, or chest pain. Colon cancer often causes diarrhea, constipation, and blood in the stool.

Some cancers may not have any symptoms at all. In certain cancers, such as pancreatic cancer, symptoms often do not start until the disease has reached an advanced stage.

The following symptoms can occur with most cancers:

• Chills
• Fatigue
• Fever
• Loss of appetite
• Malaise
• Night sweats
• Weight loss

Exams and tests.

Like symptoms, the signs of cancer vary based on the type and location of the tumor. Common tests include the following:

• Biopsy of the tumor
• Blood tests (which look for chemicals such as tumor markers)
• Bone marrow biopsy (for lymphoma or leukemia)
• Chest x-ray
• Complete blood count (CBC)
• CT scan
• MRI scan

Most cancers are diagnosed by biopsy. Depending on the location of the tumor, the biopsy may be a simple procedure or a serious operation. Most patients with cancer have CT scans to determine the exact location and size of the tumor or tumors.

A cancer diagnosis is difficult to cope with. It is important, however, that you discuss the type, size, and location of the cancer with your doctor when you are diagnosed. You also will want to ask about treatment options, along with their benefits and risks.

It's a good idea to have someone with you at the doctor's office to help you get through the diagnosis. If you have trouble asking questions after hearing about your diagnosis, the person you bring with you can ask them for you.

Treatment.

Treatment varies based on the type of cancer and its stage. The stage of a cancer refers to how much it has grown and whether the tumor has spread from its original location.

• If the cancer is confined to one location and has not spread, the most common treatment approach is surgery to cure the cancer. This is often the case with skin cancers, as well as cancers of the lung, breast, and colon.
• If the tumor has spread to local lymph nodes only, sometimes these can be removed.
• If surgery cannot remove all of the cancer, the options for treatment include radiation, chemotherapy, or both. Some cancers require a combination of surgery, radiation, and chemotherapy.
• Lymphoma, or cancer of the lymph glands, is rarely treated with surgery. Chemotherapy and radiation therapy are most often used to treat lymphoma.

Although treatment for cancer can be difficult, there are many ways to keep up your strength.

If you have radiation treatment, know that:

• Radiation treatment is painless.
• Treatment is usually scheduled every weekday.
• You should allow 30 minutes for each treatment session, although the treatment itself usually takes only a few minutes.
• You should get plenty of rest and eat a well-balanced diet during the course of your radiation therapy.
• Skin in the treated area may become sensitive and easily irritated.
• Side effects of radiation treatment are usually temporary. They vary depending on the area of the body that is being treated.

If you are going through chemotherapy, you should eat right. Chemotherapy causes your immune system to weaken, so you should avoid people with colds or the flu. You should also get plenty of rest, and don't feel as though you have to accomplish tasks all at once.

It will help you to talk with family, friends, or a support group about your feelings. Work with your health care providers throughout your treatment. Helping yourself can make you feel more in control.

Hereditary diseases.

Many hereditary diseases are passed on within families from one generation to the next. Just as children may inherit normal features such as brown eyes or curly hair from one or both parents, children can also inherit certain disorders. 
Whether or not a specific trait or disorder is inherited is determined by hereditary material called "genes." Genes are the units of hereditary material. They contain coded instructions which direct the development of every cell and tissue in the human body. You might think of genes as blueprints, specifying how the body will develop and function.

Thousands of genes are found on thread-like structures, called chromosomes, which are located in the center or "nucleus" of each cell. Genes and chromosomes exist in pairs. At the time of conception, each parent contributes one gene and one chromosome from each of his or her gene and chromosome pairs. The genes and chromosomes from each parent combine into new pairs which determine the traits a child inherits.

Most often, genes produce normal traits. Sometimes, however, a gene becomes altered from its original form. A gene that is thus changed is called a "mutant" gene. Although researchers know that mutations occur, the reasons for their occurrence is not completely understood. Some mutations are not harmful, but most often a mutant gene functions improperly and causes a disorder, malfunction, or malformation within the body. Mutations can occur in any generation. If a spontaneous mutation occurs, it is then possible for a child to be the first family member to get a genetic disorder such as Marfan syndrome, even though both parents are normal. 
Many common diseases can be caused by mutant genes. In many cases, you can manage some of those diseases just by keeping fit and staying healthy. In the extreme cases such as breast cancer a woman may lose her entire breast in the attempt to save her life. Many women may opt for breast implants. The feeling they get from breast augmentation before and after the cancer is a significant change in their mood and gaining back their self confidence. After all, how a woman feels about herself is really an important thing in these cases.

There are present multiple variations of a gene (called alleles) at the same genetic location.. For most locations, each individual possesses two alleles, one derived from each parent. If the two alleles are identical, the individual is saidto be homozygous; if they are different, the individual is heterozygous. 
In addition to mutations, the "inheritance pattern" or the way in which genetic traits or disorders are expressed also varies. The Marfan syndrome follows a pattern of inheritance called "autosomal dominant inheritance." "Autosomal" means the inheritance is linked to any chromosome other than those which determine the sex of the child. "Dominant" means the effects of the Marfan gene dominate or override the effects of the normal gene in the pair. Therefore, if one parent contributes the Marfan gene and one parent contributes a normal gene, the child will inherit the Marfan disorder. There is a 50% chance during each pregnancy that the affected parent will pass on the Marfan gene and the child will get the Marfan syndrome. There is, of course, also a 50% chance that the affected parent will pass on his or her normal gene, in which case the child will not get the disorder. 
It is important to remember that parents have no control over which genes they pass on to their children, and, therefore, should not feel at fault if one of their children inherits a disorder such as the Marfan syndrome.