CANCER




cancer has a no.of causes. one of these is incorrect information in the genetic meterial of a cell. when a cell duplicates its genetic meterial during the interphase S (synthesis) stage, rarely a mistake can occur. the exact copying of the code can be disrupted by external factors such as excessive exposure to certain chemicals (smoke, asbestos), radiation (radio active meterials), x-rays and even some viruses. this is called a mutation.
                when the genetic code governing cell division is affected, cells continue to grow and do not go into interphase. they keep dividing uncontrollably. this result in a cluster of cells called a tumor. all the cells of the tumor contain the same genetic misinformation, and some leave the tumor and travel to the other parts of the body. they go to other sites and produce more tumors we cell these other tumors at different sites metastases and when the defective cells spread they metastasize to other parts of the body.
                   cancer can occur in any tissue and a no.of terms have developed to define these cancers. tumors developing from epithelial tissue are called carcinomas;those coming from connective tissue, like bone are called sarcomas. cancer-causing agents are called carcinogens. some of the most serious cancers in humans are lung-cancer resulting from cigarette smoking, colorectal canceer caused by exessive red meat in the diet and breast cancer. the cause of breast cancer appears to be related to a gene located on chromosome number 17, which is responsible for hereditary susceptability to the disease.


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