Bacterial Genetics Flashcards
What is horizontal gene transfer (HGT)?
Horizontal gene transfer (HGT) is the movement of genetic material between organisms, distinct from vertical gene transfer, which occurs through reproduction.
What are the three main mechanisms of horizontal gene transfer in bacteria?
Conjugation, Transduction, and Transformation.
What was Frederick Griffith’s experiment, and what did it demonstrate?
Griffith’s 1928 experiment with Streptococcus pneumoniae demonstrated the “transforming principle,” showing that genetic material could be transferred between bacteria.
What did Avery, MacLeod, and McCarty discover in 1944?
They identified DNA as Griffith’s transforming principle, proving that DNA is the molecule responsible for genetic inheritance.
What is bacterial conjugation?
A process where genetic material is transferred from an F+ donor cell to an F- recipient cell via a pilus.
What are bacteriophages, and how do they contribute to horizontal gene transfer?
Bacteriophages are viruses that infect bacteria, sometimes transferring bacterial DNA through transduction.
Conjugation requires a physical connection via a pilus.
Conjugation requires a physical connection via a
pilus.
Generalized transduction can transfer any bacterial gene, while specialized transduction
transfers only specific genes near the site of lysogeny.
Transformation involves the uptake of
free DNA from the environment.
Plasmids are extra-chromosomal DNA molecules that can carry
antibiotic resistance genes.
Plasmids must be compatible to coexist in the same bacterial cell.
A: True – Incompatible plasmids cannot be stably inherited together.
Lytic bacteriophages integrate their DNA into the bacterial genome.
False – Lysogenic bacteriophages integrate their DNA, while lytic phages immediately kill the host.
Transformation only occurs in Gram-negative bacteria.
False – Transformation can occur in both Gram-positive and Gram-negative bacteria.
Specialized transduction transfers random fragments of bacterial DNA.
False – Specialized transduction transfers only genes adjacent to the prophage site.
The enzyme that cleaves DNA at the oriT site during conjugation is called __________.
Prophage.
The bacterial structure required for conjugation is called a __________.
Pilus
The process by which bacteria take up DNA from their surroundings is called __________.
Transformation.
Which of the following is NOT a method of horizontal gene transfer?
A) Transduction
B) Transformation
C) Mutation
D) Conjugation
A: C) Mutation.
What role does a fertility (F) plasmid play in conjugation?
A) It contains the genes necessary for pilus formation and DNA transfer.
B) It encodes antibiotic resistance genes.
C) It allows bacteria to uptake free DNA.
D) It integrates into the host genome.
A: A) It contains the genes necessary for pilus formation and DNA transfer.
Which bacteriophage lifecycle results in immediate lysis of the host cell?
A) Lysogenic
B) Lytic
C) Specialized
D) Generalized
A: B) Lytic.
Which bacterial genus is commonly used in transduction experiments with P1 phage?
A) Staphylococcus
B) Pseudomonas
C) Escherichia
D) Bacillus
A: C) Escherichia.
A researcher notices that bacteria grown in a medium containing extracellular DNA develop antibiotic resistance. What process is likely occurring?
Transformation
A bacterium infected with a lysogenic phage later begins to lyse and release new viral particles. What has happened?
The prophage has been excised from the genome, triggering the lytic cycle.
