How many times do DNA strands synthesize mRNA in a lifetime? Do they get recycled after protein synthesis?
DNA is often transcribed on an “as needed” basis and mRNA does not hang around very long. In fact single stranded RNA is very labile which is why the cell is smart to make mRNa from a much more stable molecule like DNA (RNA has a 3’OH which makes it susceptible to degradation while DNA does not). The best example is the immune system: Right away when you get infected you have an innate immune response which signals to the cell to transcribe mRNA to make proteins like cytokines and chemokines that help ward off infection and alert immune cells to it. Once the signal to make these proteins dies down the transcription factors responsible for them slow down and the mRNA isn’t made any more. The next time an infection happens it gets turned back on and the mRNA is transcribed again.
