DNA Structure: Definition, Discovery, Structure and Function

DNA (deoxyribonucleic acid) is a molecule that determines the trait of living organisms. We all possess traits that are inherited from our parents through genes. These genes are made up of nucleic acids and proteins. The DNA Structure consists of nitrogenous bases, phosphate groups and pentose sugar linked with bonds. DNA is a long polymer that is defined based on the number of nucleotides present. For example, E.coli has 4.6 × 106 bp nucleotides and humans have 3.3 × 109 bp.

In DNA, there are two types of nucleotide bases i.e., Purines (Adenine and Guanine) and Pyrimidines (Cytosine, Uracil and Thymine). Apart from inheriting genetic information, DNA also synthesizes protein. You can check NCERT Solutions for Class 12 Biology Chapter 6 for a better understanding of the concept. We have provided detailed information on DNA Structure in this article. Read on to find out about its definition, discovery, structure and function.

DNA Structure: Definition

DNA (deoxyribonucleic acid) is a molecule that is composed of long-chain polynucleotides carrying genetic traits from parents to offspring. This is found in prokaryotic and eukaryotic cells. This is one of the important macromolecules essential for living organisms. The two DNA strands that coil on each other to form a double helix are known as polynucleotides. DNA acts as genetic material in living organisms. In the case of viruses, RNA acts as genetic material. For example, HIV contains RNA. DNA is the predominant genetic material and the DNA present in the mitochondria are called as mitochondrial DNA. Similarly, plastids have DNA that play important role in photosynthesis.

Characteristics of DNA

It should conduct replication.
It should be stable.
It should possess the process of mutation essential for evolution.
It should not change with age, life cycle or any physiological changes.

DNA Structure: Discovery

The DNA was first identified by Johannnes Friedrich Miescher in 1869 on white blood cells. Later, James Watson and Francis Crick discovered double helix DNA molecule. The main focus of their discovery was base pairing of two strands of polynucleotides. The features of double-helix DNA molecule are as follows:

It is composed of two polynucleotide chains.
It has anti-parallel polarity. For example, one chain will have 5′—-3′ and the other will have 3′—–5′.
Two bases are linked with hydrogen bond.
The Adenine is linked with Thymine by double hydrogen bond. Likewise, Guanine is linked with Cytosine by three hydrogen bond.
Therefore, the two chains are coiled together to form a double helix.

DNA Structure

The DNA structure includes three important components i.e., nitrogenous base, pentose sugar and phosphate group. There are two types of nitrogenous bases, namely Purines (Adenine and Guanine) and Pyrimidines (Cytosine, Uracil and Thymine).

Nitrogenous base is linked to pentose sugar to form an nucleoside such as adenosine or deoxyadenosine, guanosine or deoxy guanosine, cytidine or deoxycytidine and uridine or deoxythymidine.
A corresponding nucleotide is formed when a phosphate is linked to 5′ -OH of a nucleoside.
Then, two nucleotide are linked to dinucleotide through phosphodiester linkage.
Therefore, more such nucleotides are linked to form a polynucleotide chain.

Download NCERT Solutions for Class 12 Biology Chapter 6 PDF

Function of DNA Structure

DNA stores genetic material which possess hereditary information that are passed from parents to their offspring. In eukaryotic organisms, the DNA is found in chromosomes and in case of prokaryotes, DNA is found in cytoplasm. Apart from storing genetic material, it is involved in the following processes:

Replication
Mutation
Transcription
Gene Therapy
DNA fingerprinting
Human Genome Project

FAQs Regarding DNA Structure

The frequently asked questions on DNA Structure are given below:

Q. What is DNA?
A. DNA is a long polymer of deoxyribonucleotides that determines the genetic traits of living organisms.

Q. What is the full form of DNA?
A. The full form of DNA is Deoxyribonucleic acid.

Q. What is the length of DNA?
A. The length of DNA in case of humans is 3.3 × 109 bp.

Q. What is the structure of DNA?
A. The DNA structure includes three important components i.e., nitrogenous base, pentose sugar and phosphate group. There are two types of nitrogenous bases, namely Purines (Adenine and Guanine) and Pyrimidines (Cytosine, Uracil and Thymine).

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