DNA is composed of 2 strands, the wind about each other. Every strand has actually repeating units of a nitrogenous base, deoxyribose sugar, and also a phosphate group. There are number of interactions present within a strand and also between 2 strands the stabilize the DNA.

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Covalent bond (intrastrand bonds)

Each strand consists of the following:

Base (Adenine, Thymine, Guanine, Cytosine)Deoxyribose sugarPhosphate group

There are four bases: Adenine and Guanine (purines); Cytosine and Thymine (Pyrimidines). Purines have two carbon-nitrogen rings while pyrimidines have a solitary carbon-nitrogen ring. Thus, there room four various nucleotides that deserve to be integrated into DNA.

Based on which base is attached, the nucleotides are called 2’-deoxyadenosine triphosphate, 2’-deoxycytidine triphosphate, 2’-deoxyguanosine triphosphate, or 2’-deoxythymidine triphosphate. Every of these bases is connected to 1’-carbon the the deoxyribose sugar.

In one unattached and cost-free nucleotide, there is a triphosphate team on the 5’-carbon that the deoxyribose sugar. However, when a nucleotide is integrated into a DNA strand, that loses 2 of the phosphate groups and also only one phosphate team is included to the DNA strand.


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This addition involves formation of a covalent bond dubbed the phosphodiester bond. This is formed in between the 5’-phosphate team of one nucleotide and the 3’-OH team of an additional nucleotide developing a sugar-phosphate backbone that DNA.

Hydrogen bonds

The hydrogen bonds between the basic pairs type the twin helical structure of DNA. There is no exchange or sharing of electron in hydrogen binding as seen in covalent or ionic bonds. Hydrogen bonds happen over short distances and also can be conveniently formed and also broken. Return individually each hydrogen bond is lot weaker than the covalent bond, they have the right to stabilize the twin helix because of their large numbers.

This pairing is very specific: adenin pairs with thymine and also cytosine pairs through guanine. This selective pairing is referred to as ‘complementary basic pairing’. A-T pair creates two hydrogen bonds, if C-G pair develops three. The sugar-phosphate chains kind the backbone of the ladder-like DNA structure and these basic pairs type the rungs. The broad of each of this ‘rungs’ space the exact same as it requires one purine (A or G) and one pyrimidine (C or T) base.

Stacking interactions

a) Hydrophobic effects

DNA has actually an interesting setup wherein the non-polar, uncharged bases are current in the inner of the structure, when the negatively fee phosphates are current on the outside. Together the cellular atmosphere is aqueous and also polar, the hydrophobic bases in the inner of the helix are maintained away indigenous the surrounding water and the hydrophilic heads room exposed and also interact through the exterior water. This property rises the solubility of DNA in water.

b) van der Waals forces

The nitrogenous bases stack upon one another are spaced based on their valve der Waals distance. Van der Waals distance is the street at which two molecules space attracted to each other. If this distance reduces, the electron of the 2 molecules may overlap resulting in repulsion. These forces are an extremely distance dependent and are inversely proportional to the 6th power of distance (r6 ). Return a single van der Waals interaction has actually a very little effect on the all at once structure of DNA, the net impact of number of interactions lead to an extensive stability.

c) Ionic interactions

The electrostatic (ion-ion) repulsion of the negatively fee phosphates ~ above the outside can do DNA potentially very unstable. However, magnesium ion (Mg2+) and cationic proteins in addition to arginine and lysine residues communicate with the negatively charged teams in the DNA and also stabilize it.

The strength and also stability of DNA stacking interactions has been scientifically verified by demonstrating that the use of compound (urea, formamide) that interfere v hydrogen bonds do not separate the strands completely, suggesting the existence of added forces at work.


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Written by

Dr. Surat P

Dr. Surat graduated through a Ph.D. In cell Biology and Mechanobiology native the Tata institute of an essential Research (Mumbai, India) in 2016. Before her Ph.D., Surat studied because that a Bachelor of scientific research (B.Sc.) level in Zoology, throughout which she to be the receiver of one Indian Academy of scientific researches Summer Fellowship to examine the proteins affiliated in AIDs. She to produce feature write-ups on a wide range of topics, such as medical ethics, data manipulation, pseudoscience and also superstition, education, and human evolution. She is passionate around science communication and writes write-ups covering all areas of the life sciences.


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P, Surat. 2019. Interactions That hold DNA Together. betterworld2016.org, perceived 09 November 2021, https://www.betterworld2016.org/life-sciences/Interactions-That-Hold-DNA-Together.aspx.