cancer
Risk Factors for Cancer
Genes and chromosomes
An Chromosome Abnormalities may increase the risk of cancer. For example, people with the most common type of Down syndrome, who have three instead of the usual two copies of chromosome 21, have a 12 to 20 times higher risk of developing Abnormalities (mutations) affecting critical genes are believed to contribute to the development of cancer. These genes produce proteins that regulate growth and alter cell division and other basic cell properties. Gene mutations causing cancer may result from the damaging effects of chemicals, sunlight, medications, viruses, or other environmental agents. In some families, these abnormal cancer-causing genes are inherited. The two major categories of genes involved with cancer are Oncogenes Tumor suppressor genes , which causes Breast Cancer and X-rays Sunlight Toxins at work, in the air, or in chemicals (for example, in tobacco smoke) Infectious agents (for example, certain viruses) Tumor suppressor genesnormally suppress the development of cancers by coding for proteins that repair damaged DNA or suppress the growth of cancerous cells. Cancer is more likely when DNA damage impairs tumor suppressor gene function, allowing affected cells to multiply continuously. Suppressor gene mutations, inherited from a parent, may underlie a certain percentage of cases of breast cancer, usually occurring at a young age and in multiple family members. 