- Which one of the following proteins is essential for both the initiation of DNA replication as well as the continued
advance of the replication fork?
(1) ORC (2) Geminin
(3) Cdc45 (4) Cdc6
Introduction
DNA replication in eukaryotic cells is a tightly regulated and complex process involving numerous proteins. Among these, Cdc45 (Cell Division Cycle protein 45) plays a pivotal role. It is essential not only for the initiation of DNA replication but also for the continued progression of the replication fork during S phase. This dual function distinguishes Cdc45 from other replication factors that act specifically at one stage.
What is Cdc45?
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Cdc45 is a conserved protein found in all eukaryotes.
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It is a critical component of the CMG helicase complex, which includes Cdc45, the Mcm2-7 helicase, and the GINS complex.
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The CMG complex is the active helicase that unwinds DNA at the replication fork, enabling DNA polymerases to synthesize new strands.
Role of Cdc45 in DNA Replication
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Initiation of DNA Replication:
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Cdc45 is recruited to replication origins during the transition from G1 to S phase.
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It helps activate the Mcm2-7 helicase by forming the CMG complex, which is necessary for origin firing and replication fork establishment.
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Continued Fork Progression:
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Once the replication fork is established, Cdc45 remains associated with the replisome.
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It stabilizes the helicase and coordinates interactions with other replication proteins, ensuring efficient DNA unwinding and synthesis.
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Cdc45 also interacts with PCNA and DNA polymerases, facilitating replication fork advance.
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Why Other Proteins Are Not Correct
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ORC (Origin Recognition Complex):
Involved in licensing replication origins but not in fork progression. -
Geminin:
Regulates replication licensing by inhibiting Cdt1, preventing re-replication; not involved in fork progression. -
Cdc6:
Functions in origin licensing during G1 phase but does not participate in replication fork progression.
Supporting Evidence from Research
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Structural and biochemical studies demonstrate that Cdc45 is necessary for both the formation of the initiation complex and the active helicase function during elongation.
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Mutations in Cdc45 impair both origin firing and replication fork progression, causing genome instability.
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Cdc45 interacts with multiple replisome components, highlighting its role in maintaining fork integrity.
Summary Table
| Protein | Function in DNA Replication | Role in Initiation | Role in Fork Progression |
|---|---|---|---|
| ORC | Origin licensing | Yes | No |
| Geminin | Licensing inhibitor | No | No |
| Cdc6 | Origin licensing | Yes | No |
| Cdc45 | CMG helicase component; initiation and elongation | Yes | Yes |
Final Answer
(3) Cdc45
Keywords
Cdc45, DNA replication initiation, replication fork progression, CMG helicase, eukaryotic DNA replication, replication origin firing, replisome, DNA unwinding, genome stability, cell cycle proteins
Conclusion
Cdc45 is a vital protein in eukaryotic DNA replication, uniquely required for both the initiation of DNA synthesis at replication origins and the continued advance of the replication fork during elongation. As an integral part of the CMG helicase complex, it ensures efficient DNA unwinding and coordination of replication machinery, safeguarding genome integrity throughout S phase.
33 Comments
Manisha choudhary
July 29, 2025Done sir 👍🏻
Divyanshi Vaishnav
July 29, 2025Sir explained this very well in the class, I understood it easily
Priyanka choudhary
July 29, 2025The right answer is cdc45, because of this helicase activity ko active krta h and DNA ko open krne m help krta hai jisse replication aage forword hota hai
Khushi Vaishnav
July 29, 2025The correct answer is Cdc45 ,
Initiation of dna to activate the helicase complex allow to unwind DNA at origin and continue advance of replication during elongation
Aman Choudhary
July 29, 2025Cdc45 attach with Mcm and initiate replication class me bhi acche se bataya tha sir aapne
Surbhi Rajawat
July 29, 2025Cdc 45 is very crucial because DNA polymerase alpha binds with it.
Mansukh Kapoor
July 29, 2025The correct answer is option 3rd because cdc45 helps into initiation of the DNA replication and continuous advancement of replication fork
Ankita Pareek
July 30, 2025Cdc45,is the component of cmg complex and participate in initiation as well as fork progression
Divya Mandhania
July 30, 2025Opcdc45 is correct option
anurag giri
July 30, 2025Ans 3 bcoz Cdc45 is a conserved protein in eukaryotes.
The CMG complex is the active helicase that unwinds DNA at the replication fork, enabling DNA polymerases to synthesize new strands
Sonam Saini
July 30, 2025DNA application ki starting aur application frok ki continuously growth donon ke liye compulsory protine h to answer is CDC 45
Dharmpal Swami
July 30, 2025Cdc 45 is a key component bcs
Convert the pre replicative complex into the initiation complex and also play a critical role in elongation phase
Soni
July 30, 2025Cdc-45 is most crucial among bcz it recruit dna polymerase alpha and also have bind to dna polymerase alpha
Soniya Shekhawat
July 30, 2025Cdc-45 is most crucial among bcz it recruit dna polymerase alpha and also have bind to dna polymerase alpha
Asha gurzzar
July 30, 2025Cdc6 and orc play crucial role in initiation in eukaryotes ,but cdc45 plays both role
Swati Choudhary
July 30, 2025Cdc-45 is right protein( understood in class)
Manisha gujar
July 30, 2025Option 3 is correct
Kajal
July 30, 2025Answer is cdc45
Juber Khan
July 30, 2025Ans 3 is right bcz cdc45 essential for initiation of dna replication and also for continued progression of replication fork
Cmg complex~ cdc45+mcm helicase+Gins
Sneha Kumawat
July 30, 2025Cdc 45 initiation and elongation
Anisha jakhar
July 30, 2025Cdc45 is the correct answer.
Vanshika Sharma
July 30, 2025CDC -45It is important in euk dna replication bcz it is req for both initiaton of dna synthesis and continuation of replication fork
Santosh Saini
July 30, 2025Option 3rd is correct because it is a critical component of the cmg complex ( cdc45, mcm 2-7 ,and gins )CMG complex unwind DNA at the replication fork for synthesis new strand
Priti Khandal
July 30, 2025Cdc45 Option 3 rd right
Priya khandal
July 30, 2025Cdc 45
Mitali Saini
July 31, 2025Cdc 45 is correct option
Khushi Agarwal
July 31, 2025Cdc45 essential hai for both –
Initiation (CMG helicase assembly)
Fork progression (DNA unwinding during elongation)
Aafreen
July 31, 2025ANS-3 Cdc-45
Alec Joseph
July 31, 2025correct ans is 3 because cdc45 protein is responsible for both initiation of DNA replication and continous fork progression.
shruti sharma
August 1, 2025cdc45 is correct
Anjani sharma
August 5, 2025Cdc 45 as it responsible for initiation and fork progression
Varsha Tatla
August 3, 2025Wright answer is cdc45
Anita Choudhary
August 27, 2025Cdc45 is correct answer because it help activate the MCM 2 -7 helicase by forming CMG complex which is necessary for Replication fork establishment .