During DNA replication, why is it that t | Class 12 Biology Chapter Molecular Basis of Inheritance, Molecular Basis of Inheritance NCERT Solutions

While replicating the entire DNA molecule to keep the whole molecule stabilized does not open in one go because it would be highly expose energetically. Actually unwinding creates tension in the molecule as uncoiled parts. Helicase enzyme acts on the double strand at ori site of DNA and a small stretch is unzipped also called unwind. Immediately, it is held and stabilized by single strand binding proteins. And the exposed strands are copied as a point of unwinding moves and ahead in both directions. Then it gives the appearance of Y- shaped structure which is known as replication fork.

Two functions of monomer units of NTPs are as follows:

1. They pair up with the exposed nucleotides of the template strand and make phosphodiester linkages and release a pyrophosphate.
2. Hydrolysis of this pyrophosphate by enzyme pyrophosphatase releases energy that will facilitate making hydrogen bonds between free nucleotide and bases of the template strand.