DNA replication begins when DnaA proteins bind to sequences within the origin of replication knows as DnaA box sequences. These sequences serve mainly as recognition sites for DnaA proteins. A separation in the AT rich region forms caused by the DNA bending around the DnaA protein complex. Once the AT regions are separated DnaA proteins recruit DNA Helicase. DNA Helicase breaks the double stranded DNA into single stranded DNA by breaking the hydrogen bonds. DNA Helicase travels in a 5’ to 3’ direction forming a 2 replication forks. The unwinding caused by the DNA Helicase causes positive supercoiling and as a result topoisomerase II or also known as DNA gyrase is positioned ahead of the DNA Helicase as serves by alleviating the positive supercoiling. …show more content…
These short strands prime or jumpstart the process of DNA replication. The leading strand contains 1 single primer at the origin of replication while the lagging strand contains multiple primers. The enzyme known as DNA polymerase is then responsible for the synthesis of the leading and lagging strands. There are 5 distinct polymerases involved in E. coli, however DNA polymerase III is mainly responsible for the DNA replication. In the synthesis of the leading strand the RNA primers produced by primase allow for the DNA polymerase III to begin synthesizing a complimentary daughter strand of DNA. Nucleotides are attached to the 3’ end of each primer in a 5’ to 3’ direction. This attachment is catalyzed by the DNA polymerase III. In reference specifically to the leading strand, the continuous synthesis is carried out by the production of 1 RNA primer at the origin of replication where we then see DNA polymerase III attach nucleotides in the 5’ to 3’ direction all while sliding down the opening of the replication fork. In regards to the lagging strand, DNA is also synthesized in a 5’ to 3’ direction, however it travels in the direction away from the replication