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Questions and Answers
What is one of the functions of plasmids?
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?
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)?
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?
How do nonconjugative plasmids transfer?
What is the function of dissimilation plasmids?
What is the function of dissimilation plasmids?
What is a characteristic of transposons?
What is a characteristic of transposons?
What can be a result of transposon insertion?
What can be a result of transposon insertion?
What can be coded by more complex transposons?
What can be coded by more complex transposons?
What is the result of a prophage detaching from a lysogenized bacterial cell?
What is the result of a prophage detaching from a lysogenized bacterial cell?
What is the main difference between generalized transduction and specialized transduction?
What is the main difference between generalized transduction and specialized transduction?
What is the function of the F factor in a conjugative plasmid?
What is the function of the F factor in a conjugative plasmid?
What is the role of the r-determinant in an R factor?
What is the role of the r-determinant in an R factor?
What is the outcome of widespread use of antibiotics in the presence of R factors?
What is the outcome of widespread use of antibiotics in the presence of R factors?
What is the characteristic of transducing particles in generalized transduction?
What is the characteristic of transducing particles in generalized transduction?
What is the function of R factors in bacteria?
What is the function of R factors in bacteria?
What is the type of transduction that involves the transfer of specific regions of the chromosome near the attachment site?
What is the type of transduction that involves the transfer of specific regions of the chromosome near the attachment site?
What is the primary mechanism by which conjugation occurs between bacterial cells?
What is the primary mechanism by which conjugation occurs between bacterial cells?
What is the function of the F factor in E. coli?
What is the function of the F factor in E. coli?
What is the result of conjugation between an Hfr cell and an F- cell?
What is the result of conjugation between an Hfr cell and an F- cell?
What is the primary mechanism of transduction?
What is the primary mechanism of transduction?
What is the difference between the lytic cycle and the lysogenic cycle of bacteriophage multiplication?
What is the difference between the lytic cycle and the lysogenic cycle of bacteriophage multiplication?
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?
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?
What is the primary function of plasmids?
What is the primary function of plasmids?
What is the name of the process by which bacterial cells can acquire new genes and thereby become resistant to antibiotics?
What is the name of the process by which bacterial cells can acquire new genes and thereby become resistant to antibiotics?
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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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