Master the Structure of DNA

DNA stands for Deoxyribonucleic Acid. It is a type of molecule that comprises of some genetic instructions used in the growth, development, functionalities as well as reproduction in almost all organisms. It is stated that every cell has the same instruction as that of the DNA. This topic is under the Biology section.

The DNA has a defined structure. All details about the structure are provided below in this article.


The DNA is a polymer and it consists of a group of monomer known as Nucleotide.

The Nucleotide again is comprised of a Sugar group, a Phosphate group and a base of Nitrogen.

The Nitrogen bases are of four types, they are as follows:

  • Thymine (T)
  • Adenine (A)
  • Cytosine (C)
  • Guanine (G)


Figure below shows the structure of the different nitrogen bases:

The structure of the Nucleotide is given in the figure:

The DNA consists of a chain of Nucleotides that is called Polynucleotides. A Nucleotide is attached with another forming a bond known as the Phosphodiester Bond. This process also involves in the release of a water molecule. One sugar molecule of 3’C bonds with the Phosphate Group that is attached with another sugar having 5’C. Therefore, that is the reason it is called 5’C- 3’C Phosphodiester Bond.

A chain of Polynucleotide has a bonding with another chain and forms a molecule that is double stranded. The energy that is required during its formation is fulfilled by the DNA itself. The energy comes from Nucleotides namely, dATP, dGTP, dCTP, dTTP.


The Double- Helix Model by Watson and Crick

The Double Helix model or the modern molecular structure of the DNA was discovered by James Watson and Francis Crick in the year 1953.

According to them, bonding is between A and T along with two Hydrogen bonds and there are three Hydrogen bonds between C and G. The strand contains the Phosphate and Sugar groups and hence they are the supporting structure of the DNA.


Some more aspects of the DNA:


  • The structure of the DNA is 3-D and has a pair of mutually twisted strands. DNA is a right handed Helix.
  • The diameter of the DNA is said to be 20 nanometer. The adjacent base pair distance is .34 nanometer.
  • The complete distance of the Helix is 3.4 nanometer.
  • Major and Minor grooves are present is the DNA.
  • The sequence of the base is not the same along the polynucleotide chain. The base sequence contains the genetic information.
  • Core and Backbones are two components of DNA. Core consists of the nitrogenous bases and the backbone is composed of the sugar and phosphate.

The double helix structure by Watson and Crick is given in the following figure:


This is an important topic for all the boards like CBSE, ICSE and other state boards too. Hope this article was interesting as well as informative.


About the author:

With a degree in Engineering, Saswati Ghosh is a content writer by profession. She is passionate about creative writing and blogging along with an interest in reading and part-time teaching. She is presently exploring all about the digital education with Byju’s-the Learning App.

Email-id: [email protected]

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