GENE TRANSFER IN BACTERIA: Recombination
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Questions and Answers

What is the primary function of the rec genes in E. coli?

  • To regulate the SOS system
  • To initiate conjugation
  • To produce enzymes for homologous recombination (correct)
  • To repair DNA damage through the process of transformation

    • What type of recombination typically results in insertions or deletions?

  • Illegitimate recombination
  • Homologous recombination
  • Nonhomologous recombination (correct)
  • Conjugation

    • What is the term for the genetic material transferred from one bacterium to another?

  • Recombinant DNA
  • Exogenote (correct)
  • Genome
  • Endogenote

    • Which of the following is NOT a mechanism of genetic transfer between bacterial cells?

    <p>Recombination</p> Signup and view all the answers

    What is the primary function of the SOS system?

    <p>To respond to DNA damage by inducing genes involved in repair</p> Signup and view all the answers

    What is the term for a bacterium that has received genetic material from another bacterium?

    <p>Recombinant</p> Signup and view all the answers

    What is the function of the RecA protein?

    <p>To facilitate homologous recombination</p> Signup and view all the answers

    Which of the following bacteria is naturally competent to take up exogenous DNA?

    <p>All of the above</p> Signup and view all the answers

    What is the primary consequence of a mutation that does not result in a phenotypic change?

    <p>No alteration in the structure and function of the protein</p> Signup and view all the answers

    What is the term for the process of changing the position, time, or order of something in a genetic structure?

    <p>Mutation</p> Signup and view all the answers

    What is the result of a point mutation that involves a single nucleotide change?

    <p>Only a single amino acid difference in the synthesized protein</p> Signup and view all the answers

    What type of mutation is characterized by a substitution that does not change the amino acid in the protein sequence?

    <p>Silent mutation</p> Signup and view all the answers

    What is the term for the severity or harmfulness of a disease or poison?

    <p>Virulence</p> Signup and view all the answers

    What is the result of genetic changes in an organism?

    <p>Obtaining specific properties</p> Signup and view all the answers

    What type of mutation involves a single nucleotide change?

    <p>Point mutation</p> Signup and view all the answers

    What is the outcome of an organism that has undergone mutation?

    <p>The organism becomes a mutant</p> Signup and view all the answers

    What is the primary function of the F factor plasmid?

    <p>To facilitate the transfer of genetic material between cells</p> Signup and view all the answers

    What is the main characteristic of plasmids?

    <p>They replicate independently and are physically separated from the chromosomal DNA</p> Signup and view all the answers

    What is the function of colicins encoded by the Col plasmid?

    <p>To kill other bacteria, providing a competitive advantage</p> Signup and view all the answers

    What is the primary function of the TOL plasmid?

    <p>To break down unusual organic compounds</p> Signup and view all the answers

    What is a common trait of plasmids?

    <p>They are always circular and double-stranded</p> Signup and view all the answers

    What is the result of conjugation between bacteria?

    <p>The transfer of genetic material from one bacterium to another</p> Signup and view all the answers

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

    <p>To facilitate the transfer of genetic material from a donor to a recipient cell</p> Signup and view all the answers

    What is a common result of plasmid transfer between bacteria?

    <p>Functional alterations in recipient cells, such as antibiotic resistance</p> Signup and view all the answers

    What is the mechanism by which DNA is taken up by the bacterium during transformation?

    <p>One strand of DNA is degraded while the other is taken up by the cell</p> Signup and view all the answers

    What is the role of RecA protein in homologous recombination?

    <p>It mediates recombination with homologous regions of the bacterial chromosome</p> Signup and view all the answers

    What is the primary function of bacteriophages in gene transfer?

    <p>To introduce foreign DNA into the bacterial cell</p> Signup and view all the answers

    What is the characteristic of a temperate phage?

    <p>It replicates within the bacterial genome</p> Signup and view all the answers

    What is the result of a lytic cycle in a bacteriophage infection?

    <p>The bacterial cell is lysed and new phage particles are released</p> Signup and view all the answers

    What is the purpose of electroporation in gene transfer?

    <p>To induce competence in bacteria</p> Signup and view all the answers

    What is the primary function of the SOS system?

    <p>To repair DNA damage</p> Signup and view all the answers

    What is the role of membrane-bound DNA-binding proteins in transformation?

    <p>To facilitate DNA uptake by the cell</p> Signup and view all the answers

    What is the primary requirement for transduction to occur?

    <p>Similarity in bacterial types</p> Signup and view all the answers

    Which type of transduction results in the transfer of a specific DNA region?

    <p>Localized transduction</p> Signup and view all the answers

    What is the function of the tra region in the F plasmid?

    <p>Encoding transfer functions</p> Signup and view all the answers

    Which cells produce sex pilus (pili) during conjugation?

    <p>F+ cells</p> Signup and view all the answers

    What is the result of the transfer of the F plasmid during conjugation?

    <p>Conversion of an F- cell to an F+ cell</p> Signup and view all the answers

    What is the role of the F plasmid in conjugation?

    <p>Mediation of DNA transfer between unrelated cells</p> Signup and view all the answers

    What is the characteristic of generalized transduction?

    <p>Equal chances for the transfer of every single gene in bacterial DNA</p> Signup and view all the answers

    What is the function of transposable elements in the F plasmid?

    <p>Integration into the host chromosome</p> Signup and view all the answers

    Study Notes

    Gene Transfer in Bacteria

    • Gene transfer in bacteria occurs through recombination, which incorporates extrachromosomal DNA into the chromosome.
    • There are two types of recombination: homologous and nonhomologous.
    • Homologous recombination occurs between closely related DNA sequences and requires a set of enzymes produced by the rec genes.
    • Nonhomologous recombination occurs between dissimilar DNA sequences and produces insertions or deletions, requiring specialized recombination enzymes.

    Recombination

    • A part of or all of the genetic material in bacteria can be transferred from one cell to another.
    • The process involves the uptake of DNA molecules from a donor cell by a recipient cell.
    • The exogenous material from the donor cell is called the exogenote, and its response in the recipient cell is called the endogenote.
    • The newly formed bacterium is recombinant, expressing the properties of both the donor and recipient cells.

    Mechanisms of Genetic Transfer

    • There are three main ways of genetic transfer between cells: transformation, transduction, and conjugation.

    Transformation

    • Transformation is the process by which bacteria take up fragments of naked DNA and incorporate them into their genomes.
    • Competent cells are naturally capable of taking up exogenous DNA, including Haemophilus influenzae, Streptococcus pneumoniae, Bacillus spp., and Neisseria spp.

    Transduction

    • Transduction occurs only in similar bacterial types, such as Salmonella, Shigella, Escherichia, Pseudomonas, Vibrio, Proteus, Staphylococcus, and Bacillus.
    • There are two types of transduction: localized transduction, which transfers a specific DNA region, and generalized transduction, which has an equal chance of transferring any single gene in the bacterial DNA.

    Conjugation

    • Conjugation is a form of horizontal gene transfer that requires cell-to-cell contact.
    • It is a plasmid-encoded mechanism that can mediate DNA transfer between unrelated cells, even between different genera.
    • Conjugative plasmids use this mechanism to transfer copies of themselves and the genes they encode, such as those for antibiotic resistance, to new host cells.

    F Plasmid

    • F plasmid (F stands for "fertility") is a circular DNA molecule that contains genes that regulate DNA replication and transposable elements that allow the plasmid to integrate into the host chromosome.
    • The F plasmid has a large region of DNA, the tra region, containing genes that encode transfer functions.
    • Only donor cells produce sex pilus (pili), which attach to female cells and form a bridge for conjugation.

    Conjugation Process

    • The transfer of the F plasmid converts an F- recipient cell into an F+ cell.
    • The process involves the transfer of a single strand of F plasmid from the donor cell to the recipient cell via the bridge formed by the sex pilus.
    • Both cells synthesize complementary strands, resulting in both cells becoming F+.

    Mutation

    • Mutation is a change in the nucleotide sequence of DNA that alters the structure and function of the protein to be synthesized.
    • The organism that has undergone mutation is called a mutant.
    • Mutation does not always result in a phenotypic change.

    Mutation Mechanisms

    • There are two main types of mutation mechanisms: point mutations and base-pair substitutions.
    • Point mutations involve a single nucleotide change, which can result in a silent mutation, where the amino acid in the protein sequence remains the same.
    • Base-pair substitutions involve the replacement of one nucleotide base pair with another, which can have various effects on the resulting protein and the organism's phenotype.

    Plasmids

    • Plasmids are small, circular, double-stranded DNA molecules that are physically separated from chromosomal DNA and can replicate independently.
    • Plasmids can be transferred from one bacterium to another via conjugation, causing functional alterations in the recipient cells.
    • Plasmids can carry genes that provide resistance to antibiotics, heavy metals, UV, and encode toxins, hemolysins, proteases, and pigment formation.

    Main Plasmids

    • F factor (F plasmid = fertility factor) carries genes for the formation of sex pili and for the initiation of conjugation.
    • Col plasmid (colisinogenic factors) carries genes that encode colicins, which are proteins that kill other bacteria.
    • Degradative plasmids carry genes for the breakdown of unusual organic compounds.
    • Plasmids can provide a competitive advantage, facilitate the transfer of genetic material, or allow bacteria to utilize unusual substances as a source of carbon.

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    Bacterial Genetics Lecture Notes PDF

    Description

    Learn about gene transfer in bacteria, specifically the process of recombination, including homologous and nonhomologous types. Understand the role of enzymes and rec genes in E. coli.

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