DNA replication is semi-conservative
Process:

The enzyme DNA helicase is responsible for unwinding the helix by temporarily breaking the hydrogen bonds holding the two strands together
Specialized single-stranded binding proteins (SSBs) then attach to the individual strands to prevent the hydrogen bonds from reforming

Since only small areas of DNA are being unravelled at any one time, tension can form in the twist of the helix further up the line. If the tension were to become too great, the strands could break apart. To prevent this, DNA gyrase cuts the two DNA strands and allows them to swivel around each other until the increased tension has been released and then reseals the strands.

3. As soon as DNA helicase opens up the helix and the SSBs stabilize it, replication begins.
4.The junction where the two strands are yet to be unravelled is called the replication fork and replication proceeds in the direction of that fork
5.It is the enzyme DNA polymerase III that creates the new DNA strands but, certain conditions have to be met before it can begin
The enzyme is only able to add new nucleotides to the 3′ end of the strand. This means that the enzyme can only work in a 5′ to 3′ direction. As well, the enzyme is incapable of attaching itself to the template strand and simply stringing the appropriate nucleotides together.
6.Instead, another enzyme, RNA primase, must first lay down a short string of temporary RNA nucleotides to provide an attachment site for DNA polymerase III. The polymerase can then start attaching the complementary DNA nucleotides to the temporary RNA nucleotides.

	Created by Chahat Sharma over 10 years ago

Slide Set on Key Facts - Molecular Genetics, created by Chahat Sharma on 20/05/2016.