How do the genetic mutation in ONE CELL spreads to all the cells of similar type?
If you are talking about cancer, it does start with a single cell. In simple terms, genetic mutations in that cell’s DNA cause it to lose its ability to regulate the cell cycle, and it proliferates unchecked. For example, most cells require growth factor signals to bind to receptors on their cell surface in order to divide: it is an external siganl telling the cell that dividing is the appropriate thing to do. The binding of the growth factor causes a change in the receptor which triggers a series of reactions inside the cell, which ultimately leads to genes for cell division to be activated. However, if a certain protein in that series is mutated, it can remain in the “on” state even without receiving a signal from growth factors. With that G protein (called Ras) remaining “on”, it continues to cause the genes required for cell division to be transcribed and translated. In other cases, a mutation will cause a cell to secrete signaling proteins that it itself then binds and responds to
