Deoxyribonucleic Acid (DNA) AND Ribonucleic Acid (RNA)

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March 31, 2023

Why in news?

Increasing variants of the covid-19 virus and their consequences on humans.

What is DNA?

  • Genetic carrier -Deoxyribonucleic acid (DNA) is the molecule that carries genetic information for the development and functioning of an organism.
  • Two strands -DNA is made of two linked strands that wind around each other to resemble a twisted ladder a shape known as a double helix.
    • Each strand has a backbone made of alternating sugar (deoxyribose) and phosphate groups
  • The two strands are connected by chemical bonds called bases.
  • Four bases -Adenine (A), cytosine (C), guanine (G) or thymine (T).
  • Proofreading -The enzymes responsible for copying DNA, collectively known as DNA polymerases, possess error-correction property, known as ‘proofreading’.


What is RNA?

  • Ribonucleic acid (RNA) is a nucleic acid present in all living cells that has structural similarities to DNA
  • RNA is most often single-stranded
  • An RNA molecule has a backbone made of alternating phosphate groups and the sugar ribose
  • Attached to each sugar is one of four bases: adenine (A), uracil (U), cytosine (C) or guanine (G)
  • Different types of RNA in cells are messenger RNA (mRNA), ribosomal RNA (rRNA) and transfer RNA (tRNA).
  • Some RNAs are involved in regulating gene expression.
  • RNA polymerases do not possess the ability to proofread

What is the difference between DNA and RNA viruses?

DNA Virus

RNA Virus

  • The DNA virus include the members of the pox family (smallpox and chickenpox) and Hepatitis B.
  • The RNA virus include COVID-19, AIDS, polio, influenza, dengue, chikungunya, Ebola, Zika.
  • DNA viruses contain DNA as their genetic material
  • RNA viruses contain RNA as their genetic material
  • Double-stranded DNA viruses are more common than single-stranded DNA viruses
  • Single-stranded RNA viruses are more common than double-stranded RNA viruses.
  • Viral DNA is replicated inside the nucleus of the host cell
  • Viral RNA is first transcribed and then is replicated in the cytoplasm
  • DNA viruses are stable due to the lower mutation rate.
  • RNA viruses are unstable due to the higher mutation rate
  • DNA viruses shows an accurate replication.
  • RNA viruses shows an error-prone replication

Why most viruses are RNA based?

  • Most viruses are RNA based because
    • They can encode their replication machinery
    • High mutation rates
    • Error-prone nature of their polymerases
    • Acquire multiple adaptations
    • Can exist in multiple variant forms simultaneously in each host

What are the consequences of RNA viruses?

  • Survival advantage -Few odd variants possesses a survival advantage against a vaccine or a drug.
  • Such variants will undergo further natural selection and the virus will continue to proliferate.
  • Short generation time - In a very short period after infection the host’s virus population becomes enormous.
  • Affects immune system -High viral output together with the diversity overwhelms the immune system.
  • Zoonosis –The viruses can jump across species resulting in zoonosis.
  • Spread easily among newer hosts -Because the high error rate and the short generation time enable the virus to adapt to newer conditions much faster.

A zoonosis (zoonotic disease) is an infectious disease that is transmitted between species from animals to humans (or from humans to animals).



  1. The Hindu │RNA Virus
  2. National Human Genome Research Institute │DNA Virus
  3. ThoughtCo


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