mRNA plays a crucial role in protein synthesis. It carries the information for synthesis of a particular protein from the DNA to the ribosomes.
In the cell nucleus, this information is copied (transcribed ) from DNA and onto mRNA. mRNA then leaves the nucleus and enters the cytoplasm where it attaches to a ribosome.
Transfer RNA or tRNA begins to read (translate) the information on the attached mRNA and from the pool of free amino acids in the cytoplasm, fetches the amino acids that corresponds to the information, and brings them to the ribosome where they are linked together into a chain, forming the primary structure of protein.