To begin the process of DNA replication, an enzyme called Helicase breaks the weak hydrogen bonds between nitrogenous bases. This shape is called a replication fork.
After the hydrogen bonds are broken, new bases can start to be added to the original copy. Starting on the Leading or the 3'-5' strand, bases can continuously be added. The lagging or 5'-3' strand is a little trickier. DNA polymerase, the enzyme that adds nitrogenous bases, can only work in the 3'-5' direction. To make up for this on the lagging strand, DNA polymerase must work in sections. These sections are called Okazaki fragments.
After the bases are laid down, exonuclease, another enzyme, seals any gaps left in the bases. Finally, another enzyme called DNA ligase completes the backbone to create two new DNA strands.
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