DNA Structure

Nucleic acids, such as DNA and RNA, are fundamental organic substances found universally in all organisms. Comprised of nitrogenous bases, sugar molecules, and phosphate groups, these nucleic acids are intricately linked together through various bonds to form sequences. The structure of DNA, in particular, holds the blueprint for our genetic composition, serving as the foundation for the genetic information of nearly all life forms on our planet.

Delve deeper into the meaning, structure, function, discovery, and detailed diagrams of DNA in the following sections.

“DNA is a group of molecules that is responsible for carrying and transmitting the hereditary materials or the genetic instructions from parents to offsprings.”

Viruses also adhere to this pattern, as many of these entities possess either RNA or DNA as their genetic material. For instance, some viruses utilize RNA as their genetic blueprint, while others rely on DNA. Take the Human Immunodeficiency Virus (HIV) as an example, which contains RNA as its genetic material. This RNA is subsequently transcribed into DNA upon integration into the host cell.

In addition to its role in storing genetic information across all life forms, DNA serves a pivotal function in protein synthesis. Nuclear DNA, located within the nucleus of eukaryotic cells, encodes the vast majority of an organism’s genome. Meanwhile, mitochondrial DNA, inherited exclusively from the mother, handles the remainder.

Mitochondrial DNA, situated within the cell’s mitochondria, consists of approximately 16,000 base pairs in humans. It plays a crucial role in various cellular functions. Similarly, plastids possess their own DNA, which is integral to the process of photosynthesis.

Also Read: Difference between gene and DNA

Full-Form of DNA

DNA, or Deoxyribonucleic Acid, is an organic compound characterized by its unique molecular structure. It is a fundamental component found in all prokaryotic and eukaryotic cells.

Types of DNA

There are three distinct types of DNA:

1. A-DNA: This form of DNA adopts a right-handed double helix structure similar to that of B-DNA. A-DNA is observed when DNA becomes dehydrated, offering protection during extreme conditions such as desiccation. Additionally, protein binding can lead to the formation of the A-DNA structure.

2. B-DNA: The most prevalent DNA conformation, B-DNA, exists as a right-handed helix under normal physiological conditions. This form is commonly found in the majority of DNA molecules.

3. Z-DNA: In contrast to the right-handed helix of A-DNA and B-DNA, Z-DNA is characterized by a left-handed double helix structure, winding in a zig-zag pattern. Discovered by Andres Wang and Alexander Rich, Z-DNA is often located ahead of the gene’s start site. It is hypothesized to play a role in gene regulation.

DNA was initially recognized and identified by the Swiss biologist Johannes Friedrich Miescher in 1869 during his investigations into white blood cells.

The groundbreaking discovery of the double helix structure of DNA was later unveiled through experimental data by James Watson and Francis Crick. This revelation solidified the understanding that DNA serves as the storage repository for genetic information within living organisms.

For more details, you can read about the Difference between deoxyribose and ribose.

Here is the rephrased explanation for the DNA structure diagram:

The diagram illustrates the structure of DNA, delineating its various components. DNA consists of a sugar-phosphate backbone, forming the structural framework of the molecule. Embedded within this backbone are the nucleotide bases: guanine (G), cytosine (C), adenine (A), and thymine (T). These bases pair up in specific combinations, with guanine always pairing with cytosine, and adenine always pairing with thymine.

This arrangement of the nucleotide bases along the sugar-phosphate backbone forms the iconic double helix structure of DNA, essential for its role in storing and transmitting genetic information.

DNA Diagram representing the DNA Structure

Read more: Properties of DNA

The DNA’s structure resembles a twisted ladder, known as a double helix, as depicted in the above diagram. DNA, being a nucleic acid, is constructed from nucleotides, the fundamental units of all nucleic acids. Each nucleotide consists of three distinct components: a sugar molecule, a phosphate group, and nitrogen bases.

Nucleotides, the basic building blocks of DNA, comprise a sugar group, a phosphate group, and a nitrogen base. These nucleotides are linked together by the sugar and phosphate groups to form the DNA strands. There are four types of nitrogen bases in DNA: Adenine (A), Thymine (T), Guanine (G), and Cytosine (C).

The pairing of these four nitrogenous bases follows a specific pattern: Adenine (A) pairs with Thymine (T), and Cytosine (C) pairs with Guanine (G). This base pairing is crucial for the DNA’s double helix structure, resembling a twisted ladder.

The arrangement of the nitrogenous bases dictates the genetic code or the instructions encoded within the DNA molecule.

Components of DNA Structure

Among the three components of DNA structure, sugar is the one which forms the backbone of the DNA molecule. It is also called deoxyribose. The nitrogenous bases of the opposite strands form hydrogen bonds, forming a ladder-like structure.

DNA Structure Backbone

The DNA molecule is comprised of four nitrogen bases: adenine (A), thymine (T), cytosine (C), and guanine (G), which collectively constitute the structure of a nucleotide. Adenine (A) and guanine (G) are classified as purines, while cytosine (C) and thymine (T) are classified as pyrimidines.

The two strands of DNA run in opposite directions and are connected by hydrogen bonds between the complementary bases. These strands are twisted helically, with each strand forming a right-handed coil, and a single turn consisting of ten nucleotides.

The pitch of each helix is approximately 3.4 nm, resulting in a distance of 0.34 nm between two consecutive base pairs, which are the hydrogen-bonded bases of the opposing strands.

DNA coils up to form chromosomes, with each chromosome containing a single molecule of DNA. Human beings typically have twenty-three pairs of chromosomes within the nucleus of their cells. Additionally, DNA plays a crucial role in the process of cell division.