Bacteriophage

Bacteriophage

Q. 1 What occurs when a temperate bacteriophage enters a state called “lysogeny”?
 A The bacterial cell is lysed
 B Many new viruses are produced
 C Most normal bacterial function are turned off
 D The virus may become integrated into the how genome
 
Q. 1 What occurs when a temperate bacteriophage enters a state called “lysogeny”?
 A The bacterial cell is lysed
 B Many new viruses are produced
 C Most normal bacterial function are turned off
 D The virus may become integrated into the how genome
 
Ans. D

Explanation:

There are two types of bacteriopnages-”lytic” and “temperate.” The distinction is made according to the life cycle of the bacteriophage. Upon entering a bacterium, lyric phages produce phage nucleic acids and proteins, assemble many new phage particles, lyse the cell, and release the progeny phage. Temperate phages, on the other hand, can penetrate the bacterium and enter a dormant state called “lysogeny’ in which most viral genes are repressed. Bacterial functions remain active and the bacterium is not harmed. Some dormant phages replicate as plasmids, while others, such as phage lambda, become integrated into the host genome as “prophages.” The prophage DNA is replicated along with the host DNA as the bacterium grows and divides.


Q. 2

Bacteria can transfer genetic information through all of the following methods except:

 A

Through conjugation

 B

Through bacteriophages

 C

Through incorporation of part of host DNA

 D

By taking up soluble DNA fragments across their cell wall from other species

Q. 2

Bacteria can transfer genetic information through all of the following methods except:

 A

Through conjugation

 B

Through bacteriophages

 C

Through incorporation of part of host DNA

 D

By taking up soluble DNA fragments across their cell wall from other species

Ans. C

Explanation:

Genetic information can be transferred from one bacterium to another through three methods transformation, transduction and conjugation.

Methods of transfer

Mechanism

Nature of DNA transferred

Transformation

Transfer of DNA from one bacterium to another

Any gene

Transduction

Transfer of DNA from one bacterium to another by bacteriophage Any gene in generalized transduction, only selected genes in specialized transduction

Conjugation

Transfer of DNA  from one bacterium to another through sex pilus Chromosomal or plasmid DNA

 

Ref: Textbook of Microbiology By Ananthanarayan and Panicker, 6th Edition, Page 53 ; Textbook of Microbiology and Immunology By Parija, Pages 54-7


Q. 3

Conjugation does not involve –

 A

Bacteriophages

 B

HFr

 C

Fr

 D

Plasmids

Q. 3

Conjugation does not involve –

 A

Bacteriophages

 B

HFr

 C

Fr

 D

Plasmids

Ans. A

Explanation:

Ans. is ‘a’ i.e., Bacteriophage

Quiz In Between


Q. 4

Drug resistance transfer by bacteriophage involves-

 A

Transduction

 B

Conjugation

 C

Transformation

 D

Convocation

Q. 4

Drug resistance transfer by bacteriophage involves-

 A

Transduction

 B

Conjugation

 C

Transformation

 D

Convocation

Ans. A

Explanation:

Ans. is ‘a’ i.e., Transduction


Q. 5

Transfer of a portion of DNA from one bacterium to another by the bacteriophage is known as –

 A

Transformation

 B

Transduction

 C

Transcription

 D

Lysogenic conversion

Q. 5

Transfer of a portion of DNA from one bacterium to another by the bacteriophage is known as –

 A

Transformation

 B

Transduction

 C

Transcription

 D

Lysogenic conversion

Ans. B

Explanation:

Ans. is ‘b’ i.e., Tranduction


Q. 6

Bacteriophages are mostly needed for 

 A

Bacterial identification

 B

Epidemiologically

 C

As antibacterial agent

 D

Conversion property in bacteria

Q. 6

Bacteriophages are mostly needed for 

 A

Bacterial identification

 B

Epidemiologically

 C

As antibacterial agent

 D

Conversion property in bacteria

Ans. A

Explanation:

Ans. is ‘a’ i.e., Bacterial identification 

“The specificity of bacteriophage-bacterium interaction is made use of in identification and typing of bacteria”. Bacteriophage (phage)

.    Bacteriophages are viruses that infect bacteria.

.   Phages play an important role in the transmission of genetic information between bacteria by the process of transduction.

.   The presence of phage genome integrated with bacterial chromosome confer bacteria certain properties by a process known as phage conversion.

.   Phages have been used as cloning vectors in genetic manipulation.

Quiz In Between


Q. 7

Lysogenic conversion is –

 A

New properties in a bacterium due to integration of phage genome

 B

Transfer of DNA from one bacterium to another by a bacteriophage

 C

Transfer of free DNA

 D

Transfer of genome during physical contact

Q. 7

Lysogenic conversion is –

 A

New properties in a bacterium due to integration of phage genome

 B

Transfer of DNA from one bacterium to another by a bacteriophage

 C

Transfer of free DNA

 D

Transfer of genome during physical contact

Ans. A

Explanation:

Ans. is ‘a’ i.e., New properties in a bacterium due to integration of phage genome

.                                   Bacteriophage exhibit two types of life-cycle

  1. Virulent or lytic

– Replication of phage inside bacteria leads to lysis of bacteria.

  1. Temperate or nonlytic cycle

– Phage DNA becomes integrated with the bacterial chromosome and multiplies synchronously with host DNA. – Integrated phage genome is known as prophage.

– This process of integration is called as lysogeny.

– Bacteria harbouring prophage are called as lysogenic bacteria.

– The prophage confers certain new properties on lysogenic bacterium –> Lysogenic conversion or phage conversion

– This is due to synthesis of new proteins that are coded for by the prophage DNA.

–   Example is Lysogenic conversion in diphtheria bacilli, which acquire toxigenicity (virulence) by lysogenisation with the beta phage.

A lysogenic bacterium is resistant to reinfection by the same or related phages i.e., Superinfection immunity. About other options

.  Transfer of DNA from one bacterium to another by a bacteriophage is known as Transduction.

. Transfer of free DNA is Transformation

.  Transfer of genome by physical contact is conjugation.


Q. 8

Lysis of bacterial colony in culture is seen by which virus –

 A

Pox

 B

HSV

 C

Bacteriophage 

 D

CMV

Q. 8

Lysis of bacterial colony in culture is seen by which virus –

 A

Pox

 B

HSV

 C

Bacteriophage 

 D

CMV

Ans. C

Explanation:

Ans. is ‘c’ i.e., Bacteriophage 

  • Lysis of bacteria occurs due to replication of bacteriophage in the bacteria, in lytic cycle.
  • The process of lytic cycle occurs in following steps :‑

1)    Adsorption (attachment) of a phage to the surface of a susceptible bacterium by its tail.

2)    Penetration of phage nucleic acid into the bacterial cells.

3)    Synthesis of phage components.

4)    Assembly of phage components into mature infective phage particles, i.e. maturation.

5)    Release of mature progeny phage.


Q. 9

Which of the following statement is true about bacteriophage –

 A

It is a bacterium

 B

It helps in transformation

 C

It imparts toxigenicity to bacteria

 D

It transfers only chromosomal gene

Q. 9

Which of the following statement is true about bacteriophage –

 A

It is a bacterium

 B

It helps in transformation

 C

It imparts toxigenicity to bacteria

 D

It transfers only chromosomal gene

Ans. C

Explanation:

Ans. is ‘c’ i.e., It imparts toxigenicity to bacteria 

. Bacteriophage is a virus ( not bacteria) that infects bacteria.

. Bacteriophage helps in transduction ( not transformation)

. Bacteriophage can impart toxigenicity to bacteria. Example is lysogenic conversion in diphtheria bacilli, which acquires toxigenicity ( virulence) by lysogenisation with beta phage.

  • Transduction by bacteriophage is not only confined to transfer of chromosomal DNA, episomes and plasmid may

also be transduced.

Quiz In Between


Q. 10

In staphylococci, plasmid encoding beta lactamase production is transmitted by –

 A

Conjugation

 B

Transduction

 C

Transposan

 D

Transformation

Q. 10

In staphylococci, plasmid encoding beta lactamase production is transmitted by –

 A

Conjugation

 B

Transduction

 C

Transposan

 D

Transformation

Ans. B

Explanation:

Ans. is ‘b’ i.e., Transduction

o Beta lactamases are encoded by plasmids that can be transferred with the help of bacteriophage, a process called transduction.

Also know

o Most common mechanism of acquisition of antibiotic resistance in staphylococcus —* Transduction

o Most common mechanism of acquistion of antibiotic resistance in pneumococci and Neisseria -3 Transformation o Vancomycin resistance in enterococci and staphylococcus is mediated by conjugation.


Q. 11

For phage typing, how many phages of staphylococcus aureus are used ‑

 A

12

 B

15

 C

20

 D

23

Q. 11

For phage typing, how many phages of staphylococcus aureus are used ‑

 A

12

 B

15

 C

20

 D

23

Ans. D

Explanation:

Ans. is ‘d’ i.e., 23

  • Bacteriophage typing of staphylococcus is based on susceptibility of cocci to bacteriphages.
  • This is carried out by pattern method where a set of 23 standard typing phages of S. aureus is used to type staphylococcal isolates and distinguish them from one another by their patterns of susceptibility to lysis. o The phage type of a strain is known by designation of the phages that lyse it.
  • For example, if a strain is lysed by phages 83A, 84 and 85, it is called type 83A/84/85.

Q. 12

True about bacteriophage

 A

Is a virus

 B

Causes transduction

 C

Causes lysis of Bacteria

 D

All of the above

Q. 12

True about bacteriophage

 A

Is a virus

 B

Causes transduction

 C

Causes lysis of Bacteria

 D

All of the above

Ans. D

Explanation:

Ans. is d i.e., All of the above

Bacteriophage (phage)

  • Bacteriophages are viruses that infect bacteria.
  • Phages play an important role in the transmission of genetic information between bacteria by the process of transduction.
  • The presence of phage genome integrated with bacterial chromosome confer bacteria certain properties by a process known as phage conversion.
  • Phages have been used as cloning vectors in genetic manipulation.

Q. 13

Genetic information transferred by phage is called ‑

 A

Transformation

 B

Lysogenic conversion

 C

Transduction

 D

Transcription

Q. 13

Genetic information transferred by phage is called ‑

 A

Transformation

 B

Lysogenic conversion

 C

Transduction

 D

Transcription

Ans. C

Explanation:

Ans. is ‘c’ i.e., Transduction 

Quiz In Between



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