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Questions and Answers
What is the main function of a bacteriophage?
What is the name of the bacteriophage that infects Salmonella typhimurium?
What is the result of transduction in a recipient cell?
What is the component of a bacteriophage that surrounds the genetic material?
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What is the type of gene that is transferred during transduction?
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What is the term for the process by which a bacteriophage infects a bacterial cell?
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What is the process by which a bacterium takes up extracellular DNA released by a dead bacterium?
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Who discovered the process of transformation in 1928?
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What type of transformation occurs naturally in a wide variety of bacteria?
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What is the term for bacterial cells that are able to take up DNA?
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What occurs after the uptake of DNA into the competent bacterial cell?
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What is the term for a region of mismatch caused by sequence differences between the two alleles?
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What occurs when the transformed DNA is homologous to a region in the bacterial chromosome?
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Why do some bacteria preferentially take up DNA released from dead bacteria of the same or a related species?
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What is the purpose of treating cells with calcium chloride and a high temperature shock in laboratory transformation?
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What is the term for the process in which an organism receives genes from another organism without being a direct offspring?
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What is a consequence of horizontal gene transfer in bacteria?
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What is the term for the process by which bacteria acquire genes that confer antibiotic resistance?
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What is the role of competence-stimulating peptide in Streptococcus pneumoniae?
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Why is horizontal gene transfer a serious problem worldwide?
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Study Notes
Bacterial Transduction
- Transduction is the transfer of DNA from one bacterium to another via a bacteriophage, a virus that specifically infects bacterial cells.
- Bacteriophages can transfer bacterial DNA, including P22, which infects Salmonella typhimurium, and P1, which infects Escherichia coli.
- The process of transduction involves a donor cell with a his+ gene, which is packaged into a phage particle and infects a recipient cell, making it a recombinant bacterium that is his+.
Bacterial Transformation
- Transformation is the process by which a bacterium takes up extracellular DNA released by a dead bacterium, discovered by Frederick Griffith in 1928.
- There are two types of transformation: natural transformation, where DNA uptake occurs naturally, and artificial transformation, where DNA uptake occurs with the help of experimental techniques.
- Natural transformation occurs in a wide variety of bacteria, and competent cells carry genes that encode proteins called competence factors, which facilitate DNA uptake and incorporation.
Steps of Transformation
- Extracellular DNA is cut into smaller fragments, and one strand is degraded and transported into a competent bacterial cell.
- Homologous recombination can occur, and any mismatches are repaired by DNA repair enzymes.
- The transformed cell is now lys+.
Recombination
- If the transformed DNA is homologous to a region in the bacterial chromosome, it can be incorporated by homologous recombination.
- If the DNA is not homologous, it may be incorporated at a random site on the chromosome, a process called nonhomologous recombination.
Taking up DNA from the Same Species
- Some bacteria preferentially take up DNA released from dead bacteria of the same or a related species, using mechanisms such as competence-stimulating peptides or DNA uptake signal sequences.
Artificial Transformation
- Laboratory methods are used to get plasmids into cells, including treating with calcium chloride and high temperature shock, or electroporation.
Medical Relevance of Bacterial Genetic Transfer
- Horizontal gene transfer is the process of an organism receiving genes from another organism without being a direct offspring.
- This process can occur within and between species, and includes conjugation, transformation, and transduction.
- Horizontal gene transfer has contributed to the phenomenon of acquired antibiotic resistance, with genes that confer antibiotic resistance being acquired through this process.
Acquired Antibiotic Resistance
- Antibiotic resistance is a serious problem worldwide, with bacteria acquiring genes that break down antibiotics, pump them out of the cell, or block their inhibiting effects.
- Examples of antibiotic-resistant bacteria include methicillin-resistant Staphylococcus aureus (MRSA) strains, which cause serious skin infections.
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Description
Learn about the process of transduction, where DNA is transferred from one bacterium to another via a bacteriophage, and the two cycles of bacteriophage infection.
