Greetings. I have a few questions about RNA. 1-In Nirenberg's experiment (building a protein from mRNA made only of U-U-U-U-U ...), how was the protein actually built if it didn't start with AUG (the starting Codon). If the codon AUG is not neccesary for starting the building of a protein, can you please explain how the building starts otherwise ?. 2-During mRNA processing, how are the introns identified ? 3-Why are the introns there from the first place ? If they are not translated to any protein, what is their usage ? If they have no usage, is it possible that (with time, and evolution) that the introns will go from the original DNA molecule ? 4-As far as i understand, the DNA is transcripted to mRNA, which is then translated to a protein, how does the cell know when it should transceipt a certain part of DNA to mRNA and went it shouldn't (iow, when the protein that the mRNA builds is not needed). 5-Are mRNA molecules re-used after building the protein molecule (iow, if the mRNA stays in the cytoplasm, will it be re-translated .. and re-translted ... and re-translated .. ?). Thanks in advance (that's all .. for now ).