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Related Concept Videos

DNA Topoisomerases02:02

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...
Chromatin Packaging01:32

Chromatin Packaging

Each human somatic cell contains 6 billion base pairs of DNA. Each base pair is 0.34 nm long, meaning each diploid cell contains a staggering 2 meters of DNA. This long DNA strand is packed inside a nucleus measuring only 10-20 microns in diameter with the help of specialized DNA-binding proteins called histones. Together they form a compact DNA-protein complex called chromatin. The chromatin is further compacted into higher-order structures. The highest level of compaction is achieved during...
Chromatin Packaging02:21

Chromatin Packaging

Each human somatic cell contains 6 billion base-pairs of DNA. Each base-pair is 0.34 nm long, which means that each diploid cell contains a staggering 2 meters of DNA. How is such a long DNA strand packed inside a nucleus measuring only 10 - 20 microns in diameter? 
The chromatin
In combination with specialized DNA binding protein called Histones, the DNA double helix forms a compact DNA: protein complex called chromatin. The chromatin itself is further compacted into higher-order structures.
DNA as a Genetic Template02:05

DNA as a Genetic Template

Two structural features of the DNA molecule provide a basis for the mechanisms of heredity: the four nucleotide bases and its double-stranded nature. The Watson-Crick model of double-helical DNA structure, proposed in 1952, drew heavily upon the X-ray crystallography work of researchers Rosalind Franklin and Maurice Wilkins. Watson, Crick, and Wilkins jointly received the Nobel Prize in Physiology or Medicine for their work in 1962. Franklin was, controversially, excluded from the prize for...
Fixing Double-strand Breaks02:04

Fixing Double-strand Breaks

The double-stranded structure of DNA has two major advantages. First, it serves as a safe repository of genetic information where one strand serves as the back-up in case the other strand is damaged. Second, the double-helical structure can be wrapped around proteins called histones to form nucleosomes, which can then be tightly wound to form chromosomes. This way, DNA chains up to 2 inches long can be contained within microscopic structures in a cell. A double-stranded break not only damages...
Homologous Recombination02:31

Homologous Recombination

The basic reaction of homologous recombination (HR) involves two chromatids that contain DNA sequences sharing a significant stretch of identity. One of these sequences uses a strand from another as a template to synthesize DNA in an enzyme-catalyzed reaction. The final product is a novel amalgamation of the two substrates. To ensure an accurate recombination of sequences, HR is restricted to the S and G2 phases of the cell cycle. At these stages, the DNA has been replicated already and the...

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Related Experiment Video

Updated: Jul 6, 2026

Stretching Short Sequences of DNA with Constant Force Axial Optical Tweezers
08:48

Stretching Short Sequences of DNA with Constant Force Axial Optical Tweezers

Published on: October 13, 2011

Stretching an anisotropic DNA.

B Eslami-Mossallam1, M R Ejtehadi

  • 1Department of Physics, Sharif University of Technology, P.O. Box 14588-89694, Tehran, Iran.

The Journal of Chemical Physics
|April 2, 2008
PubMed
Summary
This summary is machine-generated.

We developed a perturbation theory to analyze anisotropic DNA's response to tension. Our findings show anisotropy slightly impacts the force-extension curve, behaving like an isotropic molecule with an average bending constant.

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Last Updated: Jul 6, 2026

Stretching Short Sequences of DNA with Constant Force Axial Optical Tweezers
08:48

Stretching Short Sequences of DNA with Constant Force Axial Optical Tweezers

Published on: October 13, 2011

A Novel Stretching Platform for Applications in Cell and Tissue Mechanobiology
16:46

A Novel Stretching Platform for Applications in Cell and Tissue Mechanobiology

Published on: June 3, 2014

A Simple, Robust, and High Throughput Single Molecule Flow Stretching Assay Implementation for Studying Transport of Molecules Along DNA
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Area of Science:

  • Biophysics
  • Molecular Biology
  • Polymer Physics

Background:

  • DNA's mechanical properties are crucial for its biological functions.
  • Understanding DNA's response to external forces requires accurate theoretical models.
  • Anisotropy in DNA structure may influence its macroscopic mechanical behavior.

Purpose of the Study:

  • To develop a perturbation theory for calculating the response of anisotropic DNA to external tension.
  • To quantify the contribution of DNA anisotropy to its force-extension curve.
  • To determine an effective bending constant for anisotropic DNA under tension.

Main Methods:

  • Development of a perturbation theory framework.
  • Mathematical analysis of DNA's anisotropic mechanical response.
  • Calculation of the force-extension curve considering anisotropy.

Main Results:

  • Anisotropy contributes a small, non-zero effect to the force-extension curve of DNA.
  • The anisotropic DNA behaves mechanically like an isotropic molecule.
  • An effective bending constant is derived, representing the harmonic average of soft and hard bending constants.

Conclusions:

  • DNA's anisotropic nature has a minor but measurable impact on its mechanical response to tension.
  • The concept of an effective bending constant simplifies the description of anisotropic DNA mechanics.
  • This study provides a theoretical basis for understanding the mechanical behavior of DNA with structural variations.