Question

Problems to consider with DNA replication:

Problem: DNA has to be separated into complimentary strands and the twists and tension on DNA increases on the DNA double helix is unraveled for replication.

Solution:

Answer 1

For the DNA replication, the DNA strands are needed to be separated. So, an enzyme called DNA helicase breaks the hydrogen bonds between DNA chains so that DNA polymerase can act on it. Due to this unwinding of DNA by DNA helicase a lot of tension builds up in the DNA chain.

This tension is removed by an enzyme called DNA gyrase. DNA gyrase is a topoisomerase class enzyme with four subunits. DNA gyrase binds on both of the DNA strands away from the replication bubble and create a nick or break in DNA chains. These nicks release the tension build up due to DNA unwinding. As the replication proceeds, DNA gyrase also reseals the nicks by ligating back the DNA chains.

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