Protein molecules are the expressions of a gene.
However, to get to a protein the cell must undergo two complex processes, transcription and translation. The hnRNA must be spliced to remove non coding sequences, and protected from the cellular environment with a 5' cap and poly- A tail. In the cytoplasm, the mRNA molecule hooks up with ribosomes where the protein production can start. Every three nucleotides in the mRNA molecule codes for a specific amino acid and are appropriately called a codon. The codon pairs with an anti codon of tRNA that has attached to an amino acid.