- Given below are few statements related to DNA replication Replication in eukaryotic chromosomes from the origin(s) is initiated multiple times in each cell cycle while it is initiated only once in each cell cycle at the origin in bacterial chromosome Improper reinitiation of replication in a eubacterial chromosome is prevented by hemi-methylation status of the bacterial origin
- DNA polymerase III is the major replication polymerase responsible for de novo synthesis of both leading and lagging strands of DNA in E. coli
- Rolling circle mode of replication produces
multiple units of the original molecule
Which one of the following options represents
INCORRECT statement(s)?
(1) A only (2) Both B and C
(3) Both A and D (4) B only
Statements to Evaluate
A. Replication in eukaryotic chromosomes from the origin(s) is initiated multiple times in each cell cycle while it is initiated only once in each cell cycle at the origin in bacterial chromosomes.
B. Improper reinitiation of replication in a eubacterial chromosome is prevented by hemi-methylation status of the bacterial origin.
C. DNA polymerase III is the major replication polymerase responsible for de novo synthesis of both leading and lagging strands of DNA in E. coli.
D. Rolling circle mode of replication produces multiple units of the original molecule.
Analysis of Each Statement
A.
-
In eukaryotes, each origin of replication fires once per cell cycle to ensure genome stability. Multiple origins exist on each chromosome, but each origin initiates replication only once per cycle.
-
In bacteria like E. coli, the single origin can initiate replication multiple times per cell cycle under rapid growth conditions, allowing overlapping rounds of replication.
-
Therefore, Statement A is incorrect.
B.
-
In bacteria, the origin of replication (oriC) is hemi-methylated immediately after replication.
-
The SeqA protein binds hemi-methylated DNA, preventing premature reinitiation of replication at the origin.
-
This mechanism ensures replication initiates only once per cell cycle.
-
Statement B is correct.
C.
-
DNA polymerase III is the primary replicative polymerase in E. coli, responsible for synthesizing both leading and lagging strands.
-
It performs de novo DNA synthesis only after primer formation; the primers are synthesized by primase.
-
The statement is generally accepted as correct.
D.
-
Rolling circle replication produces multiple tandem copies (concatemers) of the original circular DNA molecule.
-
This mode is used by some viruses and plasmids.
-
Statement D is correct.
Summary Table
| Statement | Correctness | Explanation |
|---|---|---|
| A | Incorrect | Eukaryotic origins fire once per cell cycle; bacteria can reinitiate multiple times |
| B | Correct | Hemi-methylation prevents premature reinitiation in bacteria |
| C | Correct | DNA Pol III synthesizes both strands in E. coli |
| D | Correct | Rolling circle replication produces multiple copies |
Final Answer
(1) A only
Keywords
DNA replication, eukaryotic replication initiation, bacterial replication origin, hemi-methylation, DNA polymerase III, rolling circle replication, replication regulation, E. coli DNA replication
Conclusion
Among the given statements, only Statement A is incorrect because eukaryotic replication origins fire once per cell cycle, whereas bacterial origins can initiate multiple times under certain conditions. Statements B, C, and D accurately describe bacterial replication regulation, polymerase function, and replication modes.
Correct option:
(1) A only
28 Comments
Asha gurzzar
July 29, 2025A will be answere,but I have doubt on d also as I don’t understand the statement d that what does it mean
Alec Joseph
July 29, 2025Option A because in bacteria origin replication can be initiated multiple times.
Asha gurzzar
July 29, 2025A will be correct answer as the statment a is incorrect,but I don’t understand the option d what does it mean… rolling circle replication means??
Aman Choudhary
July 29, 2025Mene neeche nahi dekha incorrect puch raha tha mera dimaag kharab ho gaya ki ye kese ho sakta h 😄
Sonam
July 29, 2025A and D
Surbhi Rajawat
July 29, 2025Option A is incorrect. Replication fires (starts) only once per cycle I’m both pro and eukaryotes
Ankita Pareek
July 29, 2025Option A Is incorrect
Mitali Saini
July 30, 2025I understand this explanation answer will be A only
Mansukh Kapoor
July 30, 2025The incorrect statment is 1st because euk can have multiple ori site but replication starts once at a time for one cycle
Juber Khan
July 30, 2025Statement (1) is incorrect bcz in eucaryotes multiple origin of replication exist on chromosome but each origin initiates replication only once per cycle
Realte other options. (B) Is correct after replication oric is hemi methylated in bacteria and options (c) dna poly. Synthesis primer on both strands
Divya Mandhania
July 30, 2025Option a is correct
Dharmpal Swami
July 30, 2025In eukaryotic cells,dna replication is initiated only once per cell cycle at each origin
So statement A is incorrect
Swati Choudhary
July 30, 2025Option A is incorrect .
Manisha gujar
July 30, 2025Option a
Soniya Shekhawat
July 30, 2025Option A IS BECAUSE EUKARYOTIC REPLICATION HAVE A MULTIPLE ORIGIN OF REPLICATION SITE BUT BUT DNA REPLICATION IS INITIATE ONLY ONCE IN PER CELL CYCLE
Kajal
July 30, 2025Option 1 is incorrect
Because eukaryotes origin fires once per cycle
Bacteria can reinitiate multiple times
Santosh Saini
July 30, 2025Option 1st is incorrect because replication occurs only once per cell cycle and at the specific time
Manisha choudhary
July 30, 2025Eukaryotes m multiple ARS sequence hote h but per cell cycle ori ek baar fire hoti h
Prokaryotes m single ori hoti h pr multiple times initiate kr skti h
Prokaryotes m DNA polymerase 3 main replicative enzyme h leading or lagging both strand bnata h after primer formation primase primer bnata h
Rolling circle replication some virus and plasmid m hota h original molecule ki multiple tendam copy bnata h
Anisha jakhar
July 30, 2025Incorrect statement is A. Eukaryotic DNA contain multiple ARS but replication begins at only one ARS at a time. But bacteria can initiate multiple replications in certain conditions
Khushi Agarwal
July 31, 2025Option a is correct … Statement A is wrong
Payal Gaur
July 31, 2025Statment (1) is incorrect because in eukaryotes multiple ori present but replicate ori once per cell cycle.
B. Improper reinitiation replication prevent in bacteria by hemi methylated DNA.
C. DNA polymerase 3 form both strand leading and lagging.
D. Rolling circle mode of replication produce multiple copies (plasmid)
Ruchika
July 31, 2025Options a
shruti sharma
August 1, 2025option a is correct
Mohini
August 3, 2025The answer is A only. In eukaryotes, many ARS are present, but only once per cycle is activated.
Varsha Tatla
August 3, 2025In Ekes , multiple ori sites present so, multiple rounds of replication perform but a single ori fire only at one time per cell cycle for dna stability
Thus option 1st will be absolutely wrong
Dna pol 3 is a major replicating Enz which is involve in both legging , leading strand synthesis or de novo synthesis
So,it is wright
In Rolling circle model , multiple tendon copies are formed from original dna .It occurs in virus,
Anjani sharma
August 5, 2025Incorrect statement, option A ,as in eukaryotic replication origin fires once per cycle
Komal Sharma
September 10, 2025Statement A is incorrect because eukaryotic replication origins fire once per cell cycle, whereas bacterial origins can initiate multiple times under certain conditions. Statements B, C, and D accurately describe bacterial replication regulation, polymerase function, and replication modes.
Deepika Sheoran
November 7, 2025Option A is incorrect