45. Match List I with List II
LIST I (Protein)                                                    LIST II (Function)
A. DnaA                                                                   Ι. Recognizes ori sequence; opens duplex at specific sites in origin
B. DnaB                                                                   II. Unwinds DNA
C. DnaG                                                                   III. Synthesizes RNA primers
D. DNA gyrase                                                        IV. Relieves torsional strain generated by DNA unwinding
Choose the correct answer from the options given below:
1. A-I, B-II, C-III, D-IV
2. A-II, B-III, C-IV, D-I
3. A-III, B-IV, C-I, D-II
4. A-IV, B-I, C-II, D-III

Understanding DNA Replication Proteins and Their Functions

DNA replication is a highly coordinated process involving multiple proteins that ensure accurate duplication of genetic material. Several key enzymes and proteins work together to initiate, unwind, and stabilize the DNA strand during replication.

Correct Answer: 1. A-I, B-II, C-III, D-IV

List of DNA Replication Proteins and Their Functions

Step-by-Step Role of These Proteins in DNA Replication

1. Initiation of Replication (DnaA)

• The replication process begins at a specific sequence called oriC.
• DnaA binds to oriC, causing local unwinding and creating an open complex.
• This allows helicases and other replication proteins to access the DNA strands.

2. DNA Unwinding (DnaB – Helicase)

• DnaB helicase unwinds the double-stranded DNA, separating it into single strands.
• This action requires ATP hydrolysis for energy.
• Single-stranded DNA-binding proteins (SSBs) stabilize the unwound DNA to prevent reannealing.

3. Primer Synthesis (DnaG – Primase)

• DnaG synthesizes RNA primers, providing a starting point for DNA polymerase.
• These short RNA primers are necessary because DNA polymerase cannot initiate synthesis on its own.

4. Relieving Torsional Strain (DNA Gyrase – Topoisomerase)

• As helicase unwinds the DNA, it creates supercoiling and torsional strain.
• DNA gyrase (a type of topoisomerase) relaxes these supercoils, ensuring smooth unwinding.
• This prevents DNA breakage and maintains replication efficiency.

Significance of These Proteins in DNA Replication

• Ensures accurate and efficient DNA duplication.
• Prevents strand breaks and mutations caused by tension and supercoiling.
• Facilitates the formation of the replication fork, allowing polymerase enzymes to extend new strands.

Conclusion

DNA replication is a precisely regulated process involving multiple essential proteins. DnaA, DnaB, DnaG, and DNA gyrase each play a specific role in ensuring efficient and accurate DNA synthesis. Understanding these proteins is crucial for studies in molecular biology, genetics, and biotechnology.

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