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RNA World

Ribonucleic acid was the first genetic material. The 2′-OH of nucleotide is a reactive group that makes RNA catalytic.

It is evident that essential life processes such as metabolism, translation, splicing, etc. have evolved around RNA even before DNA has evolved as a genetic material.

Structure of Ribonucleotide chain:

In RNA also each nucleotide has three component as in DNA.

  1. Nitrogenous base –

Purine: Adenine (A) and Guanine (G).

Pyrimidine – Cytosine (C) and Uracil (U)

  1. The sugar is Ribose which has an additional -OH group on the second position.
  2. Phosphate group.

The nucleoside and nucleotide are called ribonucleoside and ribonucleotide respectively.

Types of RNA:

RNA are of three types:

  • tRNA  (transfer or soluble RNA)
  • mRNA (messenger RNA)
  • rRNA (ribosomal RNA)

m-RNA:  Messenger RNA

  • It brings the genetic information of DNA transcribed on it for protein synthesis.
  • It is single stranded.
  • It is formed on specific part of DNA called structural gene as a complementary copy of one strand of it.
  • RNA forms a template for protein synthesis.

t-RNA: Transfer or Soluble RNA

  • It act as an adaptor molecule which brings amino acid and read the genetic code.
  • tRNA has a clover leaf like secondary structure but actually it is inverted L- shaped compact molecule.
  • It has an amino acid acceptor end (3′ end) and anticodon loop where the three bases are complementary to the bases of codon of particular amino acid.

r-RNA: Ribosomal RNA

  • It forms the structure of RNA. It is the most abundant RNA.
  • It also plays a catalytic role during translation.

Questions & Answers

Question

Why is DNA a better genetic material?

Ans.

DNA rather than RNA carries the hereditary genetic code in all biological life on earth. DNA is both resilient and more easily repaired than RNA. Extra -OH group on second position of carbon of sugar make the RNA more catalytic and unstable. As a result DNA serve as a more stable carrier of genetic information.

Question

Differentiate between DNA and RNA?

Answer

Difference between RNA and DNA

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