messenger RNA (mRNA) carries a transcript (copy) of the DNA's instructions out of the nucleus to the cytoplasm where it attaches to a ribosome.
transfer RNA (tRNA) begins to read (translate) the information on the attached mRNA and corresponding to this information, fetches the appropriate amino acids from the pool of free amino acids in the cytoplasm, and brings them to the ribosome where they are linked into a chain or polymer forming the primary structure of the desired protein.