Genetic Transfer in Bacteria
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Genetic Transfer in Bacteria

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Questions and Answers

What are the three methods of genetic transfer in bacteria?

  • Conjugation, Transduction, Transformation (correct)
  • Conjugation, Binary fission, Transformation
  • Binary fission, Transduction, Transformation
  • Mutation, Selection, Conjugation

    • Vertical gene transfer in bacteria occurs between individuals that are not parents and offspring.

    False

    Horizontal gene transfer enhances genetic diversity in bacteria and occurs between ________ that are not directly related.

    individuals

    Match the following methods of bacterial genetic transfer with their definitions:

    <p>Conjugation = Involves direct physical contact between bacteria Transduction = Involves the transfer of genetic material via bacteriophages Transformation = Involves uptake of DNA from the environment Vertical gene transfer = Transfer of DNA from parent to offspring</p> Signup and view all the answers

    Which of the following statements is true regarding allelic differences in bacteria?

    <p>Allelic differences can appear between different strains due to clonal reproduction.</p> Signup and view all the answers

    E.coli is noted for having a relatively consistent genome size across all strains.

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

    The genetic transfer method that involves bacteriophages is called ________.

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

    Which of the following nutrients must an auxotroph obtain from its growth medium?

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

    All bacteria can undergo conjugation.

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

    What does the F factor in E. coli refer to?

    <p>Fertility factor</p> Signup and view all the answers

    The transfer of DNA from one bacterium to another via direct contact is known as __________.

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

    Match the following auxotrophs with their respective nutrients:

    <p>Leucine auxotroph = Leucine Methionine auxotroph = Methionine Biotin auxotroph = Biotin Thiamine auxotroph = Thiamine</p> Signup and view all the answers

    During conjugation, what structure forms between the donor and recipient cells?

    <p>Conjugation bridge</p> Signup and view all the answers

    Auxotrophs can synthesize all nutrients needed for their growth.

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

    What is the role of the relaxosome during conjugation?

    <p>To recognize the origin of transfer and make a cut in the DNA.</p> Signup and view all the answers

    In E. coli, donor strains that contain an F factor are designated as __________.

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

    Which of the following statements best describes auxotrophs?

    <p>Organisms needing specific nutrients from external sources.</p> Signup and view all the answers

    What does MRSA stand for?

    <p>Methicillin-Resistant Staphylococcus Aureus</p> Signup and view all the answers

    Both simple transposition and retrotransposition result in the integration of transposable elements at new locations in the genome.

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

    Name the enzyme responsible for catalyzing the removal of a transposon and its reinsertion.

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

    Transposons can carry ___________ genes, increasing the genetic variability within bacterial populations.

    <p>antibiotic-resistance</p> Signup and view all the answers

    Match the types of transposition to their descriptions:

    <p>Simple transposition = Cut-and-paste mechanism Retrotransposition = Copy-and-paste mechanism</p> Signup and view all the answers

    What is the role of bacteriophages in transduction?

    <p>They facilitate the transfer of genomic DNA between bacteria.</p> Signup and view all the answers

    Transformation involves the transfer of DNA through direct contact between bacterial cells.

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

    Define what it means for a bacterial cell to be 'competent.'

    <p>A competent bacterial cell is able to take up extracellular DNA from its environment.</p> Signup and view all the answers

    During transformation, an extracellular nuclease cuts the DNA into smaller ______.

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

    Match the following steps of transformation with their descriptions:

    <p>1 = DNA binds to cell surface. 2 = DNA strand enters the cell. 3 = DNA aligns with the chromosome. 4 = DNA is incorporated into the genome.</p> Signup and view all the answers

    What kind of DNA can bacteria uptake during transformation?

    <p>Extracellular DNA from any source</p> Signup and view all the answers

    Horizontal gene transfer can lead to antibiotic resistance in bacteria.

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

    What is the primary function of the exporter in bacterial conjugation?

    <p>To pump T DNA and relaxase into the recipient cell</p> Signup and view all the answers

    Name one method through which bacteria can acquire antibiotic resistance via horizontal gene transfer.

    <p>Acquiring genes that break down the antibiotic.</p> Signup and view all the answers

    The process of transformation leads to the formation of a ______ region due to sequence differences.

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

    An Hfr cell can transfer its entire chromosome in a single conjugation event.

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

    Which of the following is NOT a characteristic of naturally competent cells?

    <p>They exclusively incorporate DNA at random sites.</p> Signup and view all the answers

    What happens when F factor integrates into the chromosome?

    <p>It creates an Hfr cell.</p> Signup and view all the answers

    In a conjugation event, if it occurs for a short time, only __________ will be transferred.

    <p>lac+</p> Signup and view all the answers

    What is the purpose of transduction in bacteria?

    <p>To transfer DNA via a bacteriophage</p> Signup and view all the answers

    Match the following bacterial strains with their capabilities:

    <p>F- strain = Cannot metabolize lactose or synthesize proline Hfr strain = Can metabolize lactose and synthesize proline</p> Signup and view all the answers

    Conjugation can be used for chromosome mapping in bacteria.

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

    Name the virus that infects bacterial cells and is involved in transduction.

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

    The complete E. coli chromosome takes approximately __________ minutes to transfer.

    <p>100</p> Signup and view all the answers

    Which of the following steps occurs first in the process of transduction?

    <p>Phage infects the donor cell and host DNA is digested</p> Signup and view all the answers

    Study Notes

    Genetic Transfer in Bacteria

    • Bacteria, like eukaryotes, have allelic differences that influence traits.
    • Allelic differences in bacteria are typically between strains, not species.
    • Bacterial strains often have the same allele for a gene.
    • E. coli genomes vary significantly in gene content, ranging from 4-6 Mb in size.

    Horizontal Gene Transfer

    • Horizontal gene transfer occurs between individuals that are not in a parent-offspring relationship.
    • It enhances genetic diversity in bacteria, similar to sexual reproduction in eukaryotes.

    Overview of Genetic Transfer Methods

    • Conjugation: Direct physical contact between bacteria.
    • Transduction: Transfer of DNA via bacteriophages.
    • Transformation: Uptake of extracellular DNA from a dead bacterium.

    Bacterial Conjugation: Key Players

    • Joshua Lederberg & Edward Tatum: Discovered genetic transfer in bacteria in 1946.
    • Auxotrophs: Bacteria unable to synthesize specific nutrients.
    • F factor (fertility factor): Plasmid found in donor bacteria that allows for conjugation.
    • F+ strains: Possess the F factor.
    • F- strains: Lack the F factor.

    Steps of Conjugation

    • Contact: Donor and recipient cells connect via pili, which act as attachment sites.
    • Pilus shortening: Pili shorten to bring cells closer, forming a conjugation bridge.
    • Relaxosome: Recognizes the origin of transfer on the DNA and initiates cutting.
    • Relaxase: Attaches to the cut end of the transfer (T) DNA.
    • Exporter: Pumps T DNA and relaxase into the recipient cell.
    • Replication: Both donor and recipient F factor plasmids replicate, making both cells F+.

    Mapping Using Conjugation

    • F' factors: Carry bacterial chromosomal genes that were originally integrated into the F factor.
    • Hfr cells: Result from the F factor integrating into the bacterial chromosome.
    • Hfr x F- conjugation: Transfers a portion of the Hfr chromosome, allowing for genetic mapping.

    Transduction

    • Bacteriophage: Virus that infects bacterial cells.
    • Mispackaged phage: A phage containing host cell DNA instead of phage DNA.
    • Recombination: Donor DNA integrates into the recipient cell's chromosome.

    Transformation

    • Competent cells: Bacteria able to take up extracellular DNA.
    • Naturally competent cells: Cells that naturally take up DNA.
    • Artificially competent cells: Cells made able to take up DNA through laboratory techniques.

    Steps of Transformation

    • Binding: DNA fragment binds to a cell surface receptor on the competent cell.
    • Nuclease digestion: Extracellular nuclease cuts the DNA into smaller fragments.
    • Transport: Single DNA strand enters the cell via the uptake system.
    • Homologous recombination: DNA aligns with a homologous region on the bacterial chromosome and integrates.

    Transformation Variations

    • Nonhomologous recombination: DNA might integrate randomly into the chromosome, but it's less common.
    • Species specific uptake: Bacteria tend to take up DNA released from dead bacteria of the same or related species.
    • Plasmid uptake: Some naturally competent cells can also take up plasmids.

    Horizontal Gene Transfer (HGT) Implications

    • Antibiotic resistance: HGT plays a significant role in the spread of antibiotic resistance.
    • MRSA (Methicillin-resistant Staphylococcus aureus): Strains resistant to penicillin and methicillin, causing serious skin infections.

    Transposition

    • Transposons: Small mobile DNA segments.
    • Transposase: Enzyme that catalyzes the removal and reinsertion of transposons.
    • Inverted repeats: Identical DNA sequences that run in opposite directions, flanking transposons.

    Types of Transposition

    • Simple transposition (“cut-and-paste"): Transposon is excised and inserted at a new location.
    • Retrotransposition (“copy-and-paste"): A copy of the transposon is inserted at a new location, while the original remains.

    Why Do Transposons Exist?

    • Selfish DNA Theory: Transposons increase in frequency unless they significantly harm the host.
    • Potential advantage: Transposons may carry antibiotic-resistance genes and contribute to genetic variability.

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    Description

    Explore the fascinating mechanisms of genetic transfer in bacteria, including horizontal gene transfer and its various methods. Learn about conjugation, transduction, and transformation as well as key historical figures in the study of genetics. This quiz delves into the allelic differences that shape bacterial traits and the significance of genetic diversity.

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