Sections of the DNA strand that contains the plan for assembling a single protein is called a gene. Enzymes within the cell build a mirror image of the DNA strand through a process called transcription 1 . The enzymes begin working at one end of a gene and continue to the other end building a mirror image of the gene. The starting point of a gene is a sequence of particular three nucleic acids called a start codon 2 . The ending point of a gene is marked by a particular sequence of nucleic acids called a stop codon.
Ribosomes assemble proteins from smaller building blocks called amino acids.
The codons in the mRNA strand indicate which amino acid should be added next to the protein under construction. The ribosomes read and interpret the codons on the mRNA in order and assemble the protein according to the mRNA plan copied from the original DNA strand. The protein is assembled by the ribosome in a process called translation and begins to assume its final three-dimensional shape. Proteins are assembled from the 20 available amino acids by the ribosomes. Each amino acid has unique properties including size, three dimensional shape and polarity 4 .