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Questions and Answers

What occurs during the lysogenic cycle of a bacteriophage?

The phage DNA integrates at a specific site on bacterial DNA. (correct)

Only RNA viruses can undergo this cycle.

The bacterial cell is completely lysed immediately.

The phage DNA is replicated without integration.

Which mechanism describes the transfer of DNA between two bacterial cells through direct contact?

Transduction

Transformation

Conjugation (correct)

Binary Fission

What is formed when the donor cell's F plasmid is transferred to the recipient cell during conjugation?

An F- cell

A transducing phage

An Hfr cell

An F+ cell (correct)

What is the primary role of the F pili during bacterial conjugation?

To attach the donor to the recipient cell Signup and view all the answers

In specialized transduction, which part of the bacterial chromosome is primarily involved in the genetic transfer?

The piece of chromosome close to the prophage insertion site Signup and view all the answers

What is the primary form of bacterial genetic material?

Circular DNA Signup and view all the answers

Which type of extra chromosomal DNA can replicate independently within bacteria?

Plasmid Signup and view all the answers

Which component of plasmids is responsible for antibiotic resistance?

R Plasmid Signup and view all the answers

What is transposition in bacterial genetics?

The process of transposons moving within the genome Signup and view all the answers

What is a distinguishing feature of transposons compared to plasmids?

Transposons can only move within the genome Signup and view all the answers

How many copies of an F-plasmid are typically present in a bacterial cell?

10-15 copies Signup and view all the answers

What is the function of tra genes found in plasmids?

To mobilize plasmids via conjugation Signup and view all the answers

What makes IS transposable elements distinctive?

They encode proteins required for their own transposition Signup and view all the answers

What process allows the spread of antibiotic resistance among bacteria?

Conjugation Signup and view all the answers

Which organism is known for exhibiting antigenic variation through programmed rearrangements?

N.gonorrhoeae Signup and view all the answers

How can a bacterial cell become competent to uptake naked DNA?

Treatment with calcium chloride and heat-shock Signup and view all the answers

What role do bacteriophages play in DNA transfer between bacteria?

Mediate transduction by encapsulating bacterial DNA Signup and view all the answers

Which method involves direct uptake of naked DNA by a recipient cell?

Transformation Signup and view all the answers

What is the result of a chromosome fragment being encapsulated in a phage coat?

It leads to genetic recombination in the recipient cell Signup and view all the answers

What happens to bacterial cells during the lysogenic phase after bacteriophage integration?

They may remain inactive for generations Signup and view all the answers

What mechanism involves the transfer of DNA between bacteria via a virus?

Transduction Signup and view all the answers

Which statement accurately describes transformation in bacteria?

It involves the uptake of naked DNA from the environment. Signup and view all the answers

What is a significant trait of generalized transduction?

It can transfer any gene from the donor bacterium. Signup and view all the answers

Which of the following is NOT a role of plasmids in bacteria?

DNA replication Signup and view all the answers

Which of the following best defines a non-conjugative plasmid?

A plasmid that cannot be transferred to another bacterium. Signup and view all the answers

How do specialized transduction and generalized transduction differ?

Specialized transduction only transfers certain genes; generalized can transfer any gene. Signup and view all the answers

Which term is used to describe the process where bacteria acquire DNA from their environment?

Transformation Signup and view all the answers

What can be inferred about the spread of antibiotic resistance genes in Proteus species?

Resistance can spread via multiple mechanisms, including transduction. Signup and view all the answers

What is the significance of the integrated F factor in bacterial cells?

It creates a high frequency of recombination when excised. Signup and view all the answers

During specialized transduction, what happens to the bacterial chromosome?

A piece of chromosomal DNA is excised along with the phage DNA. Signup and view all the answers

Which of the following best describes the role of F pili in bacterial conjugation?

They enable the connection between donor and recipient cells. Signup and view all the answers

What type of bacterial cells predominantly experience plasmid transfer through conjugation?

More commonly found in Gram-negative bacilli. Signup and view all the answers

In the context of DNA transfer, what occurs when a donor cell with an F plasmid connects to a recipient cell?

One strand of the plasmid is moved and replicates in the recipient. Signup and view all the answers

How does programmed rearrangement contribute to bacterial survival?

By enabling movement of genes to active sites for expression. Signup and view all the answers

What role does calcium chloride play in transforming bacterial cells?

It increases the permeability of the cell membrane to DNA. Signup and view all the answers

What happens during transduction mediated by bacteriophages?

Random bacterial DNA fragments are transferred through viral infection. Signup and view all the answers

What characterizes the lytic cycle of a bacteriophage?

The bacterial DNA can be accidentally packaged and transferred to new cells. Signup and view all the answers

How do competent cells allow for the uptake of naked DNA?

They modify their membrane structure to enhance DNA binding. Signup and view all the answers

What is the role of bacteriophages in horizontal gene transfer?

They facilitate the movement of bacterial DNA without direct contact. Signup and view all the answers

What is the mechanism by which a bacterium can acquire DNA from the environment?

Natural competence for DNA uptake. Signup and view all the answers

What is the significance of antigenic variation in bacteria?

It helps bacteria evade host immune responses. Signup and view all the answers

What mechanism allowed Proteus species to acquire antibiotic resistance genes similar to those in Pseudomonas and Escherichia?

Transduction by bacteriophages Signup and view all the answers

In what way do generalized transduction and specialized transduction differ?

Generalized transduction transfers random DNA; specialized transduction transfers specific DNA. Signup and view all the answers

Which of the following statements accurately describes transformation in bacteria?

It involves uptake of naked DNA from the environment. Signup and view all the answers

Which characteristic differentiates transposons from plasmids in terms of replication?

Transposons lack their own replication genes and rely on the host genome. Signup and view all the answers

Which component plays a critical role in bacterial conjugation?

F plasmid Signup and view all the answers

What is a significant function of the tra genes found in certain plasmids?

They code for proteins that facilitate the mobilization of plasmids between bacterial cells. Signup and view all the answers

What is the primary source of genetic material transferred during transduction?

Segment of the host's chromosome Signup and view all the answers

Which statement regarding naked DNA in transformation is true?

It can confer specific traits such as antibiotic resistance. Signup and view all the answers

Which type of plasmid is primarily responsible for carrying genes related to antibiotic resistance?

R plasmids. Signup and view all the answers

What essential property do transposons possess that enables them to integrate into the genome?

They include specialized sequences that facilitate their movement. Signup and view all the answers

Why might a bacterium prefer transformation as a means of genetic exchange?

It circumvents the need for cell-to-cell contact. Signup and view all the answers

What describes the role of bacteriophages in generalized transduction?

They randomly encapsulate host DNA. Signup and view all the answers

What best describes the typical structure of plasmids found in bacteria?

Circular double-stranded DNA capable of independent replication. Signup and view all the answers

Which characteristic of transposons is associated with their classification as 'jumping genes'?

They can move from one location in the genome to another, including plasmids. Signup and view all the answers

Which of the following statements accurately depicts the role of plasmids in bacterial genetics?

Plasmids can carry genes for antibiotic resistance, fertility, and toxins. Signup and view all the answers

What is the primary function of the 'F-plasmid' in bacteria?

To facilitate the formation of sex pili for conjugation. Signup and view all the answers

Study Notes

Bacterial Genetics

Bacterial genome: single, circular DNA molecule forming the nucleoid
Some bacteria have extra-chromosomal DNA: plasmids, transposons
Plasmids are pieces of DNA separate from the chromosome, containing an origin of replication and independently replicating
Plasmids carry antibiotic resistance (R plasmids), fertility (F plasmids), toxins, enzymes, and bacteriocin
Plasmids are used as cloning vectors in molecular biology
Plasmids can exist as various sizes and copy numbers (1-2 copies/cell, 10-15 copies/cell, etc.)
Plasmids are typically circular and closed-circular (CCC)
Some linear plasmids are unstable due to exonuclease attack
Conjugative plasmids have tra genes that mobilize plasmid from one cell to another and are transmissible
Non-conjugative plasmids can't be mobilized under known conditions
Natural plasmids exist naturally in bacteria
Artificial plasmids are modified to be used as vectors
Transposons: extra chromosomal small pieces of DNA capable of moving themselves from one location to another on the genome
They are movable elements (jumping genes)
Transposition is the process by which transposons excise and re-integrate into DNA.
Transposons often contain an enzyme called transposase
Some transposons code for drug resistance
Composite transposons contain two insertion sequences (IS elements) flanking a central region of DNA
Non-composite transposons do not have IS elements
Tn10: encodes for tetracycline resistance
Bacteria possess genes on silent storage locations which can be moved to active sites, resulting in antigenic variations and immune evasion
Method of Bacterial Gene Transfer, Within the Bacterial Cells, Transposons transfer DNA from one site on bacterial chromosome to another site or to a plasmid, subsequent transfer of the plasmid leads to spread of antibiotic resistance
Non-composite transposons: do not have IS but contain genes for transposition, antibiotic resistance or virulence
Plasmids can be important for antibiotic resistance, toxins, or enzymes, among other properties
Transduction is the transfer of DNA from one bacterium to another by a bacteriophage (virus)
Bacteriophages can have lytic or lysogenic cycles:
- Lytic cycle: bacteriophage destroys host cells
- Lysogenic cycle: bacteriophage integrates into the host genome
Conjugation: gene transfer by direct contact between bacteria cells
Conjugation requires a donor (F+ cell with F plasmid containing tra gene) and a recipient (F- cell)
F pili form a conjugation bridge enabling plasmid transfer to the recipient (F+ cell)
An Hfr (High Frequency Recombination) cell occurs when the F plasmid integrates into the host chromosome. Transfer of chromosomal DNA from the donor to the recipient cell during conjugation
Transformation: direct uptake of naked DNA by a recipient cell

Questions

Non-conjugative plasmid: a plasmid that cannot trigger the conjugation process
Transfer of DNA from donor cells to recipient cells by bacteriophage: transduction

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