05-11-2012, 01:50 PM
Bioinformatics
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An introduction of cancer
Cancer is a disease that begins in the cells of the body. In normal situations, the cells grow and divide as the body needs them. No more, no less. This orderly process is disturbed when new cells form that the body was not needed and old cells don't die when they should. These extra cells lump together to form a growth or tumor.
Defining Cancer
Cancer is a term used for diseases in which abnormal cells divide without control and are able to invade other tissues. Cancer cells can spread to other parts of the body through the blood and lymph systems.
Cancer is not just one disease but many diseases. There are more than 100 different types of cancer. Most cancers are named for the organ or type of cell in which they start - for example, cancer that begins in the colon is called colon cancer; cancer that begins in basal cells of the skin is called basal cell carcinoma.
Cancer types can be grouped into broader categories. The main categories of cancer include:
• Carcinoma - cancer that begins in the skin or in tissues that line or cover internal organs.
• Sarcoma - cancer that begins in bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue.
• Leukemia - cancer that starts in blood-forming tissue such as the bone marrow and causes large numbers of abnormal blood cells to be produced and enter the blood.
• Lymphoma and myeloma - cancers that begin in the cells of the immune system, Central nervous system cancers - cancers that begin in the tissues of the brain and spinal cord.
Origins of Cancer
All cancers begin in cells, the body's basic unit of life. To understand cancer, it's helpful to know what happens when normal cells become cancer cells.
The body is made up of many types of cells. These cells grow and divide in a controlled way to produce more cells as they are needed to keep the body healthy. When cells become old or damaged, they die and are replaced with new cells.
However, sometimes this orderly process goes wrong. The genetic material (DNA) of a cell can become damaged or changed, producing mutations that affect normal cell growth and division. When this happens, cells do not die when they should and new cells form when the body does not need them. The extra cells may form a mass of tissue called a tumor.
Causes of cancer
Cancer is a complex group of diseases with many possible causes. In this section you can learn more about the known causes of cancer, including genetic factors; lifestyle factors such as tobacco use, diet, and physical activity; certain types of infections; and environmental exposures to different types of chemicals and radiation.
Diet and exercise
Diet, physical inactivity, and obesity are related to approximately 30–35% of cancer deaths. In the United States excess body weight is associated with the development of many types of cancer and is a factor in 14–20% of all cancer deaths.
Diets that are low in vegetables, fruits and whole grains, and high in processed or red meats are linked with a number of cancers. A high salt diet is linked to gastric cancer, aflatoxin B1, a frequent food contaminate, with liver cancer, and Betel nut chewing with oral cancer. This may partly explain differences in cancer incidence in different countries for example gastric cancer is more common in Japan with its high salt diet and colon cancer is more common in the United States. Immigrants develop the risk of their new country, often within one generation, suggesting a substantial link between diet and cancer.
Infection
Worldwide approximately 18% of cancer deaths are related to infectious diseases. This proportion varies in different regions of the world from a high of 25% in Africa to less than 10% in the developed world. Viruses are the usual infectious agents that cause cancer but bacteria and parasites may also have an effect.
Radiation
Up to 10% of invasive cancers are related to radiation exposure, including both ionizing radiation and non-ionizing radiation. Additionally, the vast majority of non-invasive cancers are non-melanoma skin cancers caused by non-ionizing ultraviolet radiation.
Heredity
The vast majority of cancers are non-hereditary ("sporadic cancers"). Hereditary cancers are primarily caused by an inherited genetic defect. Less than 0.3% of the population is carriers of a genetic mutation which has a large effect on cancer risk and this cause less than 3–10% of all cancer. Some of these syndromes include: certain inherited mutations in the genes BRCA1 and BRCA2 with a more than 75% risk of breast cancer and ovarian cancer, and hereditary nonpolyposis colorectal cancer (HNPCC or Lynch syndrome) which is present in about 3% of people with colorectal cancer, among others.
Physical agents
Some substances cause cancer primarily through their physical, rather than chemical, effects on cells. A prominent example of this is prolonged exposure to asbestos, naturally occurring mineral fibers which are a major cause of mesothelioma, a type of lung cancer. Other substances in this category, including both naturally occurring and synthetic asbestos-like fibers such as wollastonite, attapulgite, glass wool, and rock wool, are believed to have similar effects.
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Causes
Cancer starts when one normal cell becomes cancerous. This happens when something disrupts the cell DNA, altering the instructional code that monitors the cell's life cycle. One or more of a variety of risk factors may contribute to the disruption.
The most common cancer risk factors are:
• Genetic predisposition -- Certain types of cancer, such as colon and breast cancer, often run in families. It is only the predisposition to cancer that is inherited. Other non-genetic (e.g. environmental) factors must be present for the cancer to develop. Having a family history of cancer does not necessarily mean you will develop cancer, but does however mean that you are at a higher risk. Knowing the risk factors and managing them can help prevent cancer.
• Estrogen exposure (women) -- A woman is at increased risk for some gynecological cancers (e.g. breast or uterine cancer) if her system is exposed to too much estrogen, as this stimulates cell proliferation in these tissues. Factors that contribute to higher estrogen exposure include early menstruation and late menopause. The risk is reduced in women who have had a baby before the age of 35. Other factors that can reduce the risk include regular exercise and a low-fat diet.
• Ionizing radiation -- Overexposure to ionizing radiation, such as X rays and nuclear radiation, can cause DNA injury that may lead to cancer.
• Ultraviolet radiation is the radiation from the sun. Ultraviolet B (UVB) rays damage cell DNA and cause 90 percent of all skin cancers. Prevention involves reducing sun exposure, wearing protective clothing and applying a sunscreen with a high SPF (Sun Protection Factor) number.
• Carcinogenic chemicals -- Chemical carcinogens such as asbestos, benzene, formaldehyde, and diesel exhaust are dangerous in high concentrations.
• Tobacco smoke -- Smoking causes 30 percent of all cancer deaths in the United States, making tobacco smoke the single most lethal carcinogen. Smoking can cause cancers in the lungs and other organs. The best way to lower the risk of lung and other cancers is to quit smoking, or never start, and to avoid exposure to secondhand smoke if you are a non-smoker.
Diagnosis
There is no single test that can accurately diagnose cancer. The complete evaluation of a patient usually requires a thorough history and physical examination along with diagnostic testing. Many tests are needed to determine whether a person has cancer, or if another condition (such as an infection) is mimicking the symptoms of cancer.
Effective diagnostic testing is used to confirm or eliminate the presence of disease, monitor the disease process, and to plan for and evaluate the effectiveness of treatment. In some cases, it is necessary to repeat testing when a person’s condition has changed, if a sample collected was not of good quality, or an abnormal test result needs to be confirmed.
Diagnostic procedures for cancer may include imaging, laboratory tests (including tests for tumor markers), tumor biopsy, endoscopic examination, surgery, or genetic testing.
The different types of laboratory tests
Clinical chemistry uses chemical processes to measure levels of chemical components in body fluids and tissues. The most common specimens used in clinical chemistry are blood and urine.
Many different tests exist to detect and measure almost any type of chemical component in blood or urine. Components may include blood glucose, electrolytes, enzymes, hormones, lipids (fats), other metabolic substances, and proteins.
Application of Bioinformatics
Bioinformatics is the use of IT in biotechnology for the data storage, data warehousing and analyzing the DNA sequences. In Bioinformatics knowledge of many branches are required like biology, mathematics, computer science, laws of physics & chemistry, and of course sound knowledge of IT to analyze biotech data. Bioinformatics is not limited to the computing data, but in reality it can be used to solve many biological problems and find out how living things works.
It is the comprehensive application of mathematics (e.g., probability and statistics), science (e.g., biochemistry), and a core set of problem-solving methods (e.g., computer algorithms) to the understanding of living systems.