DNA Replication in Microbes Practice Questions
19 free DNA Replication in Microbes practice questions for the Microbiology. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
What is the primary origin of replication in most bacteria?
- A oriC
- B oriT
- C telomere
- D centromere
Correct answer: oriC
Most bacteria initiate DNA replication at a single origin called oriC. This region contains specific sequences recognized by initiator proteins to start replication.
Which enzyme is responsible for unwinding the DNA double helix during replication?
- A DNA ligase
- B DNA polymerase
- C Helicase
- D Primase
Correct answer: Helicase
Helicase unwinds the DNA helix by breaking hydrogen bonds between base pairs. This creates single-stranded templates for replication.
Which enzyme synthesizes RNA primers during DNA replication?
- A DNA polymerase I
- B Primase
- C Ligase
- D Topoisomerase
Correct answer: Primase
Primase synthesizes short RNA primers needed to initiate DNA synthesis. DNA polymerase cannot start synthesis without these primers.
What is the direction of DNA synthesis in microbial DNA replication?
- A 3' to 5'
- B 5' to 3'
- C Both directions simultaneously
- D Random direction
Correct answer: 5' to 3'
DNA polymerase adds nucleotides only in the 5' to 3' direction. This is a fundamental rule of DNA replication.
What are Okazaki fragments?
- A Short RNA sequences that initiate DNA synthesis
- B DNA repair enzymes
- C Multiprotein complexes at the replication fork
- D Short DNA fragments on lagging strand
Correct answer: Short DNA fragments on lagging strand
Okazaki fragments are short DNA segments synthesized discontinuously on the lagging strand. They are later joined by DNA ligase.
Which enzyme joins Okazaki fragments together?
- A Helicase
- B Primase
- C DNA ligase
- D DNA polymerase III
Correct answer: DNA ligase
DNA ligase forms phosphodiester bonds between Okazaki fragments. This creates a continuous DNA strand.
Which DNA polymerase is primarily responsible for elongation in bacteria?
- A DNA polymerase I
- B DNA polymerase II
- C DNA polymerase III
- D DNA polymerase IV
Correct answer: DNA polymerase III
DNA polymerase III is the main enzyme responsible for DNA chain elongation in bacteria. It has high processivity and speed.
What is the function of DNA polymerase I in bacteria?
- A Unwinding DNA
- B Synthesizing primers
- C Removing RNA primers and filling gaps
- D Joining Okazaki fragments on the lagging strand
Correct answer: Removing RNA primers and filling gaps
DNA polymerase I removes RNA primers and replaces them with DNA nucleotides. It also plays a role in DNA repair.
Which protein stabilizes single-stranded DNA during replication?
- A SSB protein
- B DNA helicase
- C Ligase
- D Primase
Correct answer: SSB protein
Single-strand binding (SSB) proteins prevent reannealing of DNA strands. They stabilize the unwound DNA during replication.
Which enzyme relieves supercoiling ahead of the replication fork?
- A Ligase
- B Primase
- C DNA polymerase
- D Topoisomerase
Correct answer: Topoisomerase
Topoisomerase reduces torsional strain by cutting and rejoining DNA strands. This prevents excessive supercoiling during replication.
What is meant by semiconservative replication?
- A DNA is completely new
- B Only one of the two strands is replicated
- C DNA is copied randomly
- D One old strand and one new strand
Correct answer: One old strand and one new strand
In semiconservative replication, each daughter DNA molecule contains one parental strand and one newly synthesized strand. This ensures accurate genetic inheritance.
What structure forms at the site of DNA unwinding?
- A Replication bubble
- B Transcription bubble
- C Plasmid
- D Operon
Correct answer: Replication bubble
A replication bubble forms where DNA is unwound at the origin. Replication forks move outward from this region.
Which enzyme proofreads newly synthesized DNA?
- A DNA ligase
- B Replicative helicase
- C Primase
- D DNA polymerase III
Correct answer: DNA polymerase III
DNA polymerase III has 3' to 5' exonuclease activity for proofreading. This helps correct errors during DNA replication.
What is the role of the sliding clamp in DNA replication?
- A Unwinds DNA
- B Synthesizes the RNA primers
- C Breaks hydrogen bonds
- D Holds DNA polymerase on DNA
Correct answer: Holds DNA polymerase on DNA
The sliding clamp increases the processivity of DNA polymerase by keeping it attached to the DNA strand. This allows rapid and efficient replication.
Which process ensures replication occurs in both directions from the origin?
- A Unidirectional replication
- B Random replication
- C Fragmented replication
- D Bidirectional replication
Correct answer: Bidirectional replication
Replication in bacteria is bidirectional, meaning it proceeds in two directions from the origin. This increases replication efficiency.
Which component provides energy for DNA polymerization?
- A ATP
- B RNA primers
- C dNTPs
- D Proteins
Correct answer: dNTPs
Deoxyribonucleotide triphosphates (dNTPs) provide both the building blocks and energy for DNA synthesis. The release of pyrophosphate drives the reaction.
Which region of DNA signals termination of replication in bacteria?
- A Ter region
- B oriC
- C Promoter
- D Operator region
Correct answer: Ter region
The Ter region contains termination sequences where replication stops. These sequences interact with termination proteins to halt replication forks.
Which protein initiates DNA replication at oriC?
- A DnaA
- B DnaB
- C DnaC
- D SSB
Correct answer: DnaA
DnaA binds to specific sequences at oriC to initiate replication. It helps open the DNA helix for other proteins to act.
What is the main difference between leading and lagging strand synthesis?
- A Continuous vs discontinuous synthesis
- B Direction of the replication fork movement
- C Type of nucleotides used
- D Location in cell
Correct answer: Continuous vs discontinuous synthesis
The leading strand is synthesized continuously, while the lagging strand is synthesized discontinuously in fragments. This is due to the antiparallel nature of DNA.