Functions of Plasmids

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Questions and Answers

What is one of the functions of plasmids?

Catalyzing the breakdown of complex molecules

Facilitating the synthesis of proteins

Regulating cell division

Producing bactericidal substances active against other strains (correct)

What can occur when transposons insert themselves within genes of chromosomes?

Activation of gene expression

Silencing of gene expression

Enhancement of gene expression

Inactivation of gene expression (correct)

What is the function of the gene codes in insertion sequences (IS)?

Recognition sites and enzyme transposase (correct)

Gene expression and regulation

DNA repair and replication

Antibiotic resistance and toxin production

How do nonconjugative plasmids transfer?

Through inserting themselves into a conjugative plasmid Signup and view all the answers

What is the function of dissimilation plasmids?

Coding for enzymes that catalyze the breakdown of unusual sugars and hydrocarbons Signup and view all the answers

What is a characteristic of transposons?

They can move from one region of a DNA molecule to another Signup and view all the answers

What can be a result of transposon insertion?

Inactivation of a gene Signup and view all the answers

What can be coded by more complex transposons?

Toxins, antibiotic resistance, and other genes Signup and view all the answers

What is the result of a prophage detaching from a lysogenized bacterial cell?

It takes a piece of chromosomal DNA with it to another bacterial cell Signup and view all the answers

What is the main difference between generalized transduction and specialized transduction?

The regions of the chromosome transduced Signup and view all the answers

What is the function of the F factor in a conjugative plasmid?

It codes for sex pilus formation Signup and view all the answers

What is the role of the r-determinant in an R factor?

It codes for the production of enzymes that inactivate antibiotics Signup and view all the answers

What is the outcome of widespread use of antibiotics in the presence of R factors?

The development of new antibiotic-resistant strains Signup and view all the answers

What is the characteristic of transducing particles in generalized transduction?

They carry only chromosomal DNA Signup and view all the answers

What is the function of R factors in bacteria?

To confer antibiotic resistance Signup and view all the answers

What is the type of transduction that involves the transfer of specific regions of the chromosome near the attachment site?

Specialized transduction Signup and view all the answers

What is the primary mechanism by which conjugation occurs between bacterial cells?

Through direct cell-to-cell contact mediated by pili or sticky molecules Signup and view all the answers

What is the function of the F factor in E. coli?

To facilitate conjugation Signup and view all the answers

What is the result of conjugation between an Hfr cell and an F- cell?

The F- cell acquires new versions of chromosomal genes Signup and view all the answers

What is the primary mechanism of transduction?

The transfer of DNA from one bacterium to another by means of a bacteriophage Signup and view all the answers

What is the difference between the lytic cycle and the lysogenic cycle of bacteriophage multiplication?

The lytic cycle involves the release of phage particles, while the lysogenic cycle involves the integration of phage DNA into the host genome Signup and view all the answers

What is the type of transduction that occurs when a bacteriophage accidentally picks up a piece of bacterial DNA and injects it into another bacterium?

Generalized transduction Signup and view all the answers

What is the primary function of plasmids?

To provide antibiotic resistance Signup and view all the answers

What is the name of the process by which bacterial cells can acquire new genes and thereby become resistant to antibiotics?

Horizontal gene transfer Signup and view all the answers

Study Notes

Plasmid Functions

Virulence: code for exotoxins, adhesion or invasion factors, making bacteria harmless without these plasmids
Bacteriocin production: produce bactericidal substances active against other strains, used as food preservatives
Dissimilation plasmids: code for enzymes that catalyze the catabolism of unusual sugars and hydrocarbons, allowing bacteria like Pseudomonas to survive in challenging environments

Transposons

Small segments of DNA (700-40,000 bp) that can move from one region of a DNA molecule to another
Can insert themselves within genes of chromosomes, inactivating them
Often occur randomly, infrequently (once every 10^5 - 10^7 generations)
Simplest transposon: insertion sequences (IS), containing a gene that codes for recognition sites and an enzyme transposase that catalyzes the cutting and resealing of DNA
More complex transposons: contain other genes, such as toxins and antibiotic resistance

Transduction

Generalized transduction: all regions of the chromosome are transduced, only chromosomal DNA (no phage DNA) in transducing particles
Specialized transduction: only specific regions of the chromosome located near the attachment site are transduced, transducing particles carry both chromosomal DNA and phage DNA

Conjugation

Transfer of DNA between bacterial cells mediated by plasmids
Requires direct cell-to-cell contact and conjugating cells must be of opposite "mating" types
In E. coli, the F factor (fertility factor) was the first observed to transfer plasmid during conjugation
Conjugation can lead to the transfer of chromosomes, allowing F- cells to acquire new versions of chromosomal genes

Gene Transfer

Types: transformation, conjugation, and transduction

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Description

This quiz covers the different functions exhibited by plasmids, including conjugation, virulence, bacteriocin production, and dissimilation.