Related Information: They do this by translating messenger RNA (mRNA) into proteins. Messenger RNA is simply a copy of the DNA from the nucleus that is allowed to enter the cytoplasm and be used to make proteins. Ribosomes are the sites of protein synthesis, where RNA is translated into protein.When cells need large numbers of proteins, they must first build numerous ribosomes. Because protein synthesis is so important to cells, there are large numbers of ribosomes in all cells, often numbering in the hundreds or thousands.he primary function of Ribosomes is to read and translate the cell's genetic code, then reproduce (replicate) the proteins that the code represents. Without the ribosomes this coded message could not be read or replicated.