Key Points About ΦX174 Replication
88. Reproduction of Φ x 174, a single stranded DNA phage involves several steps. A few statements are given below to explain the mechanism.
A. The single stranded Φ X 174 DNA is converted into a double-stranded replicative form (RF)
B. Replication of double stranded replicative form results in the production of single stranded phages, about 50% of which are +ve sense phages and the remaining are -ve sense phages
C. Replication of the double stranded replicative form results in the production of only -ve sense phages
D. Replication of the double stranded replicative form results in the production of only +ve sense phages
Choose the option that correctly describes the process
(1) A only
(2) A and B
(3) A and C
(4) A and D
Key Points About ΦX174 Replication
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Statement A: The single-stranded ΦX174 DNA is converted into a double-stranded replicative form (RF) by host enzymes.
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This is the initial and essential step in the replication cycle. The single-stranded (+) DNA enters the host and is converted into a double-stranded circular replicative form (RF), which serves as the template for further replication.
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Statement B: Replication of the double-stranded replicative form results in the production of single-stranded phages, about 50% of which are +ve sense and the remaining are -ve sense phages.
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This is incorrect. The progeny phages produced are predominantly single-stranded +ve sense DNA, which is the genome packaged into new phage particles. The -ve sense strand serves as a template during replication but is not packaged into phage particles.
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Statement C: Replication of the double-stranded replicative form results in the production of only -ve sense phages.
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Incorrect. The packaged phage DNA is the +ve sense strand.
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Statement D: Replication of the double-stranded replicative form results in the production of only +ve sense phages.
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Correct. The progeny phages contain single-stranded +ve sense DNA identical to the original infecting genome.
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Summary
| Statement | Correctness | Explanation |
|---|---|---|
| A | Correct | ssDNA converted to dsDNA replicative form (RF) by host enzymes |
| B | Incorrect | Progeny phages are not a 50:50 mix of +ve and -ve strands |
| C | Incorrect | Phages do not package only -ve sense DNA |
| D | Correct | Progeny phages contain only +ve sense ssDNA |
Conclusion
The replication of ΦX174 involves the conversion of single-stranded DNA into a double-stranded replicative form, followed by rolling circle replication producing single-stranded +ve sense DNA packaged into progeny phages. Therefore, the correct combination of statements is:
(4) A and D
Keywords
ΦX174, single-stranded DNA phage, replicative form, rolling circle replication, +ve sense DNA, phage replication, bacteriophage lifecycle
Final answer:
(4) A and D
41 Comments
Shivani .
July 29, 2025Yes, the correct option is 4
The ssDNA converted into double stranded DNA by its host enzyme ,it’s the initial step of DNA replication .
And the progeny produced will be predominantly +ve sence SSDNA.
SO here statement A and D are correct
Priya dhakad
July 29, 2025The correct option is 4
It is so easy
Santosh Saini
July 29, 2025Yes 4th option is correct because ssDNA convert into dsDNA by host DNA polymerase and – strand act as a template for synthesis of + strand, these +strand synthesized by rolling circle mechanism, so option A and D are correct
Surbhi Rajawat
July 29, 2025The replication in this phage converts ss DNA into ds DNA each strand is then distributed into progeny.
Hence the A option is correct along with D
Mitali Saini
July 29, 2025Correct option is 4
Soniya Shekhawat
July 29, 2025Aand D IS CORRECT because in this rolling circle dna replication is appearing in which ssdna is convert into dsdna and only +ve sense dna is present in progeny hence Aand D IS CORRECT STATEMENT
Pratibha
July 29, 2025Correct option is option (4) bcz
A explains the initial step (ssDNA → RF).
D explains the final outcome (only + sense ssDNA phages).
Kajal
July 29, 2025Option 4 is correct
A and D is correct
Anisha jakhar
July 29, 2025A and D are correct statements according to rolling circle replication as ssDNA gets converted into dsDNA ( replication form). Also progeny only contain +ve sense ssDNA.
Deepika
July 29, 2025The single standard dna (ssDNA) of the phage is converted into double standard dna (ds dna)by the host cells dna polymerase enzyme.
The negative strand acts as a template to make the positive strand .
The positive strand is made using a rolling circle replication mechanism.
So both option A and D are correct.
Mohini
July 29, 2025The option D is the correct answer.
The DNA phage convert ssDNA into dsDNA and only produce +vr sense phages.
Shivani Panwar
July 29, 2025Ans is 4
Mukur Prabha Ramawat
July 29, 20254th option is correct as the statement ‘A’ and ‘D’ are the initial and final outcome of replication
Vijay Marmat
July 29, 2025The best website for csir net life science
Correct ans A&D 4
shruti sharma
July 29, 2025a and d is corrrect
Dipti Sharma
July 29, 2025The replication involves conversion of ssDNA into dsDNA , followed by rolling circle mechanism where -ve strand act as template for synthesis of +ve strand , producing +ve sense DNA packaged into progeny phages
Deepika sheoran
July 30, 2025The 4th option is correct because single standard turns into double standard dna with the help of the host dna polymerase.the negative strand is used as a model to make the positive strand.the positive strand is made using a method called rolling circle replication.so, option A and D are correct..
Mahima sharma
July 30, 2025Answer is a and d
Mahima sharma
July 30, 2025Answer is a and d rolling circle method
Khushi Vaishnav
July 30, 2025Statement A is correct because ssDNA converted to dsDNA replicative form (RF) by host enzymes
And D is correct because Progeny phages contain only +ve sense ssDNA
Mahima sharma
July 30, 2025Answer is a and d rolling circle method
👍🏻
Komal soni
July 30, 2025Yes, the correct option is 4
The ssDNA converted into double stranded DNA by its host enzyme ,it’s the initial step of DNA replication .
And the progeny produced will be predominantly +ve sence ssDNA.
SO here statement A and D are correct
Anjali Sharma
July 30, 2025Yes 4 ans is correct because ssdna is convert into ds-dna.
Deepshikha choudhary
July 30, 2025option 4 is correct : ssDNA converts into dsDNA by its host enzyme in the intitial step of replication nd progeny only contain positive sense
Priya Dhakad
July 30, 2025The option is A and d rolling circle method
Payal Gaur
July 30, 2025Option (4) A and D (ssDNA convert in to dsDNA by enzymes (rolling circle) and progeny phage contain only positive sense ssDNA)
Nilofar khan
August 16, 2025Correct answer is a and d becouse of rolling circle replication method
Niti
July 30, 2025Answer is A and D
Juber Khan
July 31, 2025Option 4 right
– single strand dna convert into double strand dna replicative form (RF) +
dsdna RF used as template to synthesis new ssdna genome
Dp
August 1, 2025Ssdna convert into ds dna
Result are positive sense
Dp
August 1, 2025Ssdna convert into ds dna
Result are positive sense
SHOBHA SHARMA
August 1, 2025Answar is the correct A and D
The single stranded is convert in to a double stranded replicative form
Resuit are +ve sense phages
Manisha choudhary
August 3, 2025Ss DNA host cell m jaayega and ss DNA ,ds DNA bnata h
-ve strand temple ki tarah kaam krti h jo +ve strand bnata h rolling circle replication method s
Asha gurzzar
August 5, 2025Yes answer a and d will be correct as single strand dna forms double strand dna so the result are in positive sense
Anita choudhary
August 22, 2025Option 4 is correct , because single stranded DNA is converted into Double stranded DNA by its host enzyme and it is the initial process of DNA REPLICATION .
And the progeny produced will be predominantly +ve sence SSDNA.
Aafreen Khan
August 23, 2025Ans -4 A and D is correct answer
ssDNA converted to dsDNA replicative form by host enzymes
Progeny phages contain only +ve sense ssDNA
By rolling method
vishal saini
September 18, 2025yes sir correct answer is 4 (A$D)
Komal Sharma
September 23, 2025The replication of ΦX174 involves the conversion of single-stranded DNA into a double-stranded replicative form, followed by rolling circle replication producing single-stranded +ve sense DNA packaged into progeny phages. Therefore, the correct combination of statements is:
(4) A and D
Mitali
November 4, 2025Option a and d
Deepika Sheoran
November 7, 2025Option 4 th is correct
Meenakshi Choudhary
November 11, 2025(4) A and D is correct