Describe Protein Synthesis

DNA is unzipped by a helicase, the gene to be encoded is transcribed to mRNA by the enzyme RNA polymerase, in mRNA the thymine base is substituted by uracil. The mRNA leave the nucleus via a nuclear pore and migrates to a ribosome on the rough endoplasmic reticulum (rER). The ribosome translates mRNA to a polypeptide using tRNA molecules. Translation occurs by a tRNA molecule, in the ribosome, complimentary to a triplet of base pairs known as a codon binding to the mRNA, each tRNA molecule has an attached amino acid unique to the codon to which it compliments. As tRNA binds the mRNA a chain of amino acids attached to each other by peptide bonds is formed, the primary structure of the resulting polypeptide is determined by the sequence of bases in the DNA which in turn gives rise to the secondary and tertiary structure. The polypeptide is formed in the rER where it undergoes post translation modifications. This is then packaged into a vesicle and migrates to the Golgi body where it undergos further modifications to form the protein. It is then packaged into a vesicle and utilised by the cell.