Chapter 14, Problem 13STP

Summary Introduction

To analyze:

The role that different enzymes play in the replication of DNA.

Introduction:

DNA is the genetic material in most living organisms. It is the information hub of the cell that contains instructions for the synthesis of proteins. The central dogma of molecular biology is that DNA undergoes replication to create copies of itself, undergoes transcription to create expressible mRNA and this mRNA undergoes translation so that protein can be formed from the information carried in mRNA.

Explanation of Solution

Stepwise involvement of enzymes in the replication of DNA:

Step 1: Initiation

DNA Helicase	It is an enzyme responsible for opening the DNA helix by breaking the hydrogen bonds present between the nitrogenous bases. Helicase enzyme requires the hydrolysis of enzymes ATP hydrolysis.
Single strand binding protein	It binds to both the separated strands of the DNA and avoids the unwinding back of DNA.
Primase	It is an enzyme responsible for synthesizing a short RNA primer which is required for the initiation of the process of replication.

Elongation

DNA pol III	It is an enzyme responsible for the addition of nucleotides in 5’-3’ direction.
Type I topoisomerase	It is an enzyme responsible for creating a nick or break in the single-strand DNA. This enzyme binds to the strand and breaks it and forms a 5’-phosphodiester bond.
Type II topoisomerase	Also known as DNA gyrase is responsible for the super coiling of the strands of DNA.
DNA pol I	Performs exonuclease activity by removing the RNA primer and also replaces the same with newly synthesized DNA.
DNA pol II	It performs the repair function. If the template is damaged then this enzyme can also replicate the DNA.

Termination:

DNA ligase

It is an enzyme that seals the gaps between the Okazaki fragments and creates one continuous DNA strand.

Conclusion

Therefore, different enzymes are performing different functions in the process of replication of DNA.