Question

What are the two general strategies for maintaining the very high degree of fidelity of DNA replication during replication itself?

Following the discovery of DNA polymerase I, what experimental evidence suggested that another enzyme is the primary enzyme of replication?

What are the features of DNA polymerase that ensure the right nucleotides are inserted?

Describe the mechanism of polymerization used by polymerases.

Answer 1

Ans:- Proofreading mechanism shown b the DNA polymerase is the important factor for fidelity of DNA replication itself. In E.Coli the mistake made occurs only for every 10⁹ to 10¹⁰ nucleotides added, but with this rate of mistakes replication would introduce errors into significant percentage of genes every generations the polymerase enzyme has an inherited mechanism of proof reading it discriminates the nucleotides between the correct and incorrect bases and depends just on the hydrogen bonds that specify the correct base pairing between complementary bases but also on the common geometry of the of the standard A=T and G C base pairs . The DNA polymerase only accomodate the correct base pairs and incorrect bases are eliminated hence the incorporation of wong base is eliminated to a large extent but this mecanism is insufficient to account for high degree of fidelity in DNA replication. fortunately the polymerase has other mechanism of proof reading for the fidelity of DNA replication and is as;

3'>5' exonuclease activity:- this mechanism double checks the incorporation of wrong base pair during polymerisation process and the nuclease activity within the polymerase permits the enzyme to remove the newly added nucleotide and is highly specific for mismatch base pairs once the mismatch base pair is removed the polymerase then moves again and this activity is known as proof reading.