Explain the role of each enzyme involved in DNA replication.

DNA replication involves the action of numerous enzymes. These are: DNA Helicase, DNA Gyrase, Single Stranded Binding Proteins, DNA Primase, DNA polymerase III, DNA polymerase I, DNA Ligase.DNA Helicase breaks the hydrogen bonds between the nitrogenous base pairs in order to unwind the double helix.DNA Gyrase prevents supercoiling of the strands: it does so by reducing the torsional strain caused by the unwinding of the double helix by Helicase. Single Stranded Binding Proteins bind to the strands to prevent re-annealing (recombining). Moreover, they prevent digestion of DNA by nucleases. DNA Primase synthesises a short RNA primer on each of the two template strands: this allows for the binding of DNA polymerase III to the template strand.DNA polymerase III joins the free nucleotides to their complementary bases in a 5' to 3' direction, thus generating a complementary strand.Because the lagging strand is being synthesised in fragments, it has numerous RNA primers. DNA polymerase I removes these primers and replaces them with DNA nucleotides. DNA Ligase joins the Okazaki fragments in the lagging strand. Now a continuous strand is formed as covalent bonds join the sugar-phosphate backbone together with a phosphodiester bond (linkage of 3' carbon atom of one sugar molecule to a 5' carbon atom of another sugar molecule).