Search research articles

ABOUT JoVE

Overview Leadership Blog JoVE Help Center

AUTHORS

Publishing Process Editorial Board Scope & Policies Peer Review FAQ Submit

LIBRARIANS

Testimonials Subscriptions Access Resources Library Advisory Board FAQ

RESEARCH

JoVE Journal Methods Collections JoVE Encyclopedia of Experiments Archive

EDUCATION

JoVE Core JoVE Business JoVE Science Education JoVE Lab Manual Faculty Resource Center Faculty Site

Terms & Conditions of Use

Related Concept Videos

DNA Topoisomerases

DNA Topoisomerases

Topoisomerases are enzymes that relax overwound DNA molecules during various cell processes, including DNA replication and transcription. These enzymes regulate positive and negative DNA supercoiling without changing the nucleotide sequence. DNA overwinding in a clockwise direction results in positively supercoiled DNA, whereas underwinding in a counterclockwise direction produces negatively supercoiled DNA.
Types and Mechanism of action
Topoisomerases are divided into two main types. Type I...

The DNA Replication Fork

The DNA Replication Fork

An organism’s genome needs to be duplicated in an efficient and error-free manner for its growth and survival. The replication fork is a Y-shaped active region where two strands of DNA are separated and replicated continuously. The coupling of DNA unzipping and complementary strand synthesis is a characteristic feature of a replication fork. Organisms with small circular DNA, such as E. coli, often have a single origin of replication; therefore, they have only two replication forks, one in...

The DNA Replication Fork

The DNA Replication Fork

An organism’s genome needs to be duplicated in an efficient and error-free manner for its growth and survival. The replication fork is a Y-shaped active region where two strands of DNA are separated and replicated continuously. The coupling of DNA unzipping and complementary strand synthesis is a characteristic feature of a replication fork. Organisms with small circular DNA, such as E. coli, often have a single origin of replication; therefore, they have only two replication forks, one in...

Replication in Prokaryotes

Replication in Prokaryotes

DNA replication has three main steps: initiation, elongation, and termination. Replication in prokaryotes begins when initiator proteins bind to the single origin of replication (ori) on the cell's circular chromosome. Replication then proceeds around the entire circle of the chromosome in each direction from the two replication forks, resulting in two DNA molecules.
Many Proteins Work Together to Replicate the Chromosome
Replication is coordinated and carried out by a host of specialized...

Replication in Prokaryotes

Replication in Prokaryotes

Replication in Prokaryotes

Replication in Prokaryotes

You might also read

Related Articles

Articles linked to this work by shared authors, journal, and citation graph.

Sort by

Same author

Repair of Single-Stranded Breaks in Hyperthermophilic DNA.

Journal of molecular biology·2025

Same author

Theoretical model, its parameters and predictions: Reply to comments on "DNA melting and energetics of the double helix".

Physics of life reviews·2018

Same author

DNA melting and energetics of the double helix.

Physics of life reviews·2017

Same author

Type II topoisomerases: Experimental studies, theoretical models, and logic: Reply to comments on "Disentangling DNA molecules".

Physics of life reviews·2016

Same author

When Computer Simulation Excels Experiment.

Biophysical journal·2016

Same author

Disentangling DNA molecules.

Physics of life reviews·2016

Search research articles

Related Experiment Video

Updated: Jun 17, 2026

Visualization of DNA Replication in the Vertebrate Model System DT40 using the DNA Fiber Technique

Visualization of DNA Replication in the Vertebrate Model System DT40 using the DNA Fiber Technique

Published on: October 27, 2011

DNA supercoiling helps to unlink sister duplexes after replication.

Alexander Vologodskii¹

¹New York University, New York, 10003, USA. alex.vologodskii@gmail.com

Bioessays : News and Reviews in Molecular, Cellular and Developmental Biology

|December 19, 2009

Summary

DNA supercoiling aids in unlinking replicated DNA. Computer simulations of linked plasmids in Escherichia coli with suppressed topoisomerase IV offer insights into this complex DNA topology mechanism.

More Related Videos

Single-Molecule Real-Time Visualization of DNA Unwinding by CMG Helicase

Single-Molecule Real-Time Visualization of DNA Unwinding by CMG Helicase

Published on: September 27, 2024

Visualizing Single-molecule DNA Replication with Fluorescence Microscopy

Visualizing Single-molecule DNA Replication with Fluorescence Microscopy

Published on: October 9, 2009

Related Experiment Videos

Last Updated: Jun 17, 2026

Visualization of DNA Replication in the Vertebrate Model System DT40 using the DNA Fiber Technique

Visualization of DNA Replication in the Vertebrate Model System DT40 using the DNA Fiber Technique

Published on: October 27, 2011

Single-Molecule Real-Time Visualization of DNA Unwinding by CMG Helicase

Single-Molecule Real-Time Visualization of DNA Unwinding by CMG Helicase

Published on: September 27, 2024

Visualizing Single-molecule DNA Replication with Fluorescence Microscopy

Visualizing Single-molecule DNA Replication with Fluorescence Microscopy

Published on: October 9, 2009

Area of Science:

Molecular Biology
Genetics
Biophysics

Background:

Newly replicated DNA molecules often become entangled, requiring mechanisms for separation.
DNA topoisomerases are enzymes that manage DNA topology by passing strands through each other.
Separating linked sister DNA duplexes is a critical step in cell division.

Purpose of the Study:

To investigate the role of DNA supercoiling in the unlinking of replicated DNA.
To elucidate less intuitive mechanisms of DNA decatenation, specifically involving type II DNA topoisomerases.
To gain insights into DNA topology simplification through computational analysis.

Main Methods:

Computer simulation of linked sister plasmids.
Analysis of DNA topology in Escherichia coli cells.
Experimental suppression of topoisomerase IV activity.

Main Results:

The study provides insights into how DNA supercoiling facilitates the unlinking of replicated DNA.
Analysis revealed the significance of topology simplification in resolving DNA catenation.
Simulations demonstrated the behavior of linked plasmids under specific enzymatic conditions.

Conclusions:

DNA supercoiling is a crucial, though not always intuitive, mechanism for resolving DNA entanglement.
Type II DNA topoisomerases play a key role in simplifying DNA topology for strand separation.
Computational approaches can illuminate complex molecular processes like DNA decatenation.