RNA World - The Genetic Material and the Origins of Life

The RNA world hypothesis suggests that RNA was the first genetic material to exist before DNA and proteins. RNA is believed to have played a dual role as both a genetic material and a catalyst for biochemical reactions. This theory provides insights into the origin of life, explaining how simple molecules could have evolved into complex living organisms. In this article, RNA world hypothesis, RNA world, and types of RNA are discussed. RNA World is a topic of the chapter Molecular Basis of Inheritance in Biology.

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This Story also Contains

1. What is the RNA World Hypothesis?
2. What Is RNA World?
3. Types of RNA
4. RNA as Genetic Material

What is the RNA World Hypothesis?

The RNA World Hypothesis proposes that RNA, not DNA, served as the first genetic material and exerted a central role in the early evolution of life on Earth. It is postulated that an RNA molecule can act as both a storage for genetic information and a bio-catalyst. Understanding the world of RNA is essential to explain the fundamental questions of the origin of life and the emergence of cellular complexity.

What Is RNA World?

According to the RNA world hypothesis, RNA (ribonucleic acid) is a very important molecule that initially performed the living purpose in all living cells. It is a nucleic acid made by nucleotides, such as sugar, a phosphate group and bases(adenine, guanine, cytosine and uracil).

Also Read-

• MCQ on RNA World
• Molecular Basis of Inheritance
• RNA Processing
• RNA Splicing

Diagram: RNA Hypothesis

The diagram below shows the flow of genetic information as per the RNA world hypothesis and Central dogma of molecular biology.

Types of RNA

• mRNA (Messenger RNA): Just carries genetic information from DNA, through ribosomes, to the synthesis of proteins.

• tRNA (Transfer RNA): tRNA transfers amino acids to the ribosome during protein synthesis.

• rRNA (Ribosomal RNA): It forms part of the ribosome, and functions in the synthesis of proteins.

RNA as Genetic Material

RNAs are also considered catalysts for major biochemical reactions in primitive cells. The presence of the 2-OH group makes them more reactive and thus a suitable biocatalyst. However, this reactive nature makes them susceptible to degradation and hence unstable. This instability gave a wider spectrum of mutation required for evolution. But being a hereditary material it should have been stable both chemically and structurally.

Eventually, these unstable molecules are now replaced by more stable hereditary molecules, such as DNA. During this evolutionary period, DNA and protein molecules came into view. These substituted RNA as the genetic material and structural component. RNA is a single-stranded hereditary molecule which stores and expresses genetic information. However, their unstable and degrading nature led to the creation of double-stranded DNA molecules that are more stable both chemically and structurally.

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