Difference Between ssDNA and dsDNA

The key difference between ssDNA and dsDNA is that ssDNA exists as a linear single chain of deoxyribonucleotides while dsDNA exists as two complementary chains of deoxyribonucleotides attached together by hydrogen bonds.

Deoxyribonucleic acid is a nucleic acid that makes heredity material of most of the living organisms. It is a polymer composed of deoxyribonucleotides. A nucleotide has three components: a deoxyribose sugar, a nitrogenous base and a phosphate group. There are four types of nitrogenous bases as adenine (A), guanine (G), cytosine (C), and thymine (T). DNA mainly exists as double stranded helix. But, some organisms, especially viruses, possess single stranded DNA.

CONTENTS

1. Overview and Key Difference
2. What is ssDNA 
3. What is dsDNA
4. Similarities Between ssDNA and dsDNA
5. Side by Side Comparison – ssDNA vs dsDNA in Tabular Form
6. Summary

What is ssDNA?

Generally, DNA exists as double stranded tightly coiled helix. But some organisms such as viruses have single stranded DNA genomes. Single stranded DNA does not have two complementary strands binding with each other. It exists as a single long strand of nucleotides.

Furthermore, viruses belonging to Group II of the Baltimore classification system such as viruses of the family Microviridae have ssDNA genomes. These single-stranded DNA viruses are abundant in seawater, freshwater, sediments, terrestrial and extreme environments, as well as metazoan-associated and marine microbial mats.

What is dsDNA?

dsDNA or double stranded DNA, as the name implies, exists as double strands. Therefore, in dsDNA, there are two complementary long strands bonded and coiled tightly with each other. There are hydrogen bonds between two strands. Hence, dsDNA is stiffer than ssDNA. Furthermore, dsDNA is more stable than ssDNA.

Moreover, dsDNA is resistant to formaldehyde reaction. In most living organisms, dsDNA makes the genome. Most importantly, in dsDNA, the total number of adenine is equal to thymine. Similarly, the total number of cytosine is similar to guanine.

What are the Similarities Between ssDNA and dsDNA?

• ssDNA and dsDNA are nucleic acids made up of deoxyribonucleotides.
• They contain deoxyribose sugar, nitrogenous bases and phosphate groups.
• Their chemical composition is similar.
• They act as the genetic material of living organisms.
• Both are prone to become damaged by strong chemicals and UV.

What is the Difference Between ssDNA and dsDNA?

ssDNA has only one strand of nucleotides while dsDNA has two complementary strands of nucleotides bonding together by hydrogen bonds. Thus, this is the key difference between ssDNA and dsDNA. Furthermore, ssDNA is less stable and stiff while dsDNA is more stable and stiff. This is another difference between ssDNA and dsDNA. Moreover, almost all living organisms contain dsDNA while only few viruses contain ssDNA. This is also an important difference between ssDNA and dsDNA.

Summary – ssDNA vs dsDNA

ssDNA has only one nucleotide strand while dsDNA has two nucleotide chains which are complementary to each other and bound together by two hydrogen bonds between adenine and thymine, and three hydrogen bonds between cytosine and guanine. Therefore, this is the key difference between ssDNA and dsDNA. Moreover, dsDNA is more stiff and stable than ssDNA. In addition, dsDNA is present in all most all organisms while ssDNA is present only in few types of viruses. This summarizes the difference between ssDNA and dsDNA.

Reference:

1. “Double-Stranded DNA.” Double-Stranded DNA – an Overview | ScienceDirect Topics, Available here.
2. “DNA Virus.” Wikipedia, Wikimedia Foundation, 13 Aug. 2019, Available here.

Image Courtesy:

1. “Genome map of the bacteriophage ΦX174 showing overlapping genes” By Emmanuel Douzery  – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “1116336” (CC0) via Pixabay