Intro To Plasmids Flashcards
What is a plasmid?
A plasmid is a small, circular, double-stranded DNA molecule that is distinct from chromosomal DNA and can provide genetic advantages such as antibiotic resistance.
What are the key structural components of a plasmid?
The origin of replication (OR), multiple cloning region (MCR), and inserted gene.
How do plasmids replicate?
Plasmid replication occurs in three stages: initiation, elongation, and termination.
What is the role of restriction enzymes in bacterial defense?
Restriction enzymes cleave DNA at specific sequences to protect bacterial cells from viral infections by destroying invasive DNA.
What is the replisome, and what is its function?
The replisome is a large protein complex that facilitates DNA replication by mediating helicase, primase, and DNA polymerase activities, creating a replication fork.
Plasmids exist in
bacteria and some eukaryotes.
The origin of replication determines where
plasmid replication begins.
Restriction enzymes function as
bacterial defense mechanisms.
Plasmid replication must be regulated to maintain
stable copy numbers.
Bacteria can transfer plasmids through
conjugation.
Plasmids are always linear DNA molecules.
False – Plasmids are typically circular.
All plasmids carry genes that provide antibiotic resistance.
False – Some plasmids carry other genes, such as those for metabolism or virulence.
Restriction enzymes always cut DNA at random sites.
False – They cut at specific recognition sequences.
Plasmid replication requires host-encoded proteins.
True – Host proteins are involved in replication along with plasmid-encoded factors.
The enzyme responsible for introducing a single-strand break in plasmid DNA during initiation is called __________.
Rep protein.
The enzyme complex responsible for DNA synthesis during plasmid replication is __________.
DNA polymerase III holoenzyme.
The bacterial structure that facilitates plasmid transfer through conjugation is called a __________.
Pilus.
Plasmid replication is regulated to maintain a fixed __________ of plasmid molecules within a bacterial population.
Concentration.
Which of the following is NOT a function of plasmids?
A) Antibiotic resistance
B) Protein synthesis
C) Virulence factor transmission
D) Metabolic adaptation
A: B) Protein synthesis.
Which enzyme cleaves DNA at specific recognition sites?
A) DNA polymerase
B) Restriction endonuclease
C) Helicase
D) Ligase
A: B) Restriction endonuclease.
Which of the following is a stage of plasmid replication?
A) Transduction
B) Initiation
C) Transcription
D) Translation
A: B) Initiation.
What prevents bacterial restriction enzymes from cutting their own DNA?
A) DNA is single-stranded
B) DNA is methylated
C) DNA is circular
D) DNA lacks an origin of replication
A: B) DNA is methylated.
A researcher inserts a foreign gene into a plasmid and introduces it into bacterial cells. What key feature of the plasmid ensures this gene is successfully expressed?
A: Multiple cloning region (MCR).
A bacterial strain contains an antibiotic-resistant plasmid. After mixing with a sensitive strain, some bacteria acquire resistance. What process likely occurred?
A: Conjugation.
