The reason why people don't get cancer all the time is because there's Hayflick limit. Hayflick limit limits the amount of time a cell divides. On the end of chromosome, there's something called a telomere that is made of CG repeats. Telomere doesn't code for anything. It only gets chopped away each time cell division takes place. It gets chopped away on the lagging strand because after RNA Primase makes RNA Primers from 3' to 5' and DNA is filled in, Ligase changes RNA primers into DNA except the last one. That's how it gets cut off. In cells like blood cells that need to constantly divide, they have an enzyme that is called telomerase. Telomerase adds telomere sequences to the end of chromosomes therefore enable cells to keep dividing.
Proto-oncogenes are normal cellular genes code for proteins that stimulate normal cell growth and division. However, they may become excessively active and mutates into Oncogenes, which cause cancer.
Tumor-suppressoe genes encode proteins that inhibit abnormal cell division. Nevertheless, they may decrease and cause cancer.
The formation of cancer starts with a malfunction cell that keeps on dividing. All the cells it produces will clump together and produce more cells. Blood veins will be drawn to the spot and provide ATP for the cancer cells. These cancer cells might enter blood veins and be transferred to other parts of the body.The chemo treatments are designed to stop processes of the cancer formation.
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