Introduction, Classification, Chemical Nature and Biological Role of Nucleic Acids : Pharmaguideline

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Introduction, Classification, Chemical Nature and Biological Role of Nucleic Acids

Purines and pyrimidines (a class of organic compounds) make up DNA, a natural chemical compound.

Nucleic acids


Purines and pyrimidines (a class of organic compounds) make up DNA, a natural chemical compound. By directing protein synthesis, nucleic acids serve as the main carriers of information in cells, which determines the inherited characteristics of any living thing. Nucleic acids are divided into two classes: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). A virus' genetic material is made up of DNA, which forms the blueprint for life. Besides living cells, it is also found in a variety of tissues in which it plays an important role in processes like protein synthesis. It is also found in all living cells. RNA is the genetic material of viruses.



A pentose sugar, phosphoric acid, and nitrogen-containing cyclic bases are the building blocks of DNA. DNA molecules contain the sugar moiety β-D-2-deoxyribose. Nitrogen is found in the following cyclic bases: adenine (A), guanine (G), cytosine (C), and thymine (T). These bases are arranged in DNA molecules in a way that affects how information is passed from generation to generation. It is made up of double-stranded helices, whose strands are complementary to one another.


A pentose sugar and some nitrogen-containing cyclic bases are also included in the RNA molecule. RNA contains sugar moiety β-D-ribose. Homocyclic bases found in RNA include adenine (A), cytosine (C), guanine (G), and uracil (U). DNA has four bases, RNA has four different ones. RNA is made up of a single strand that can fold back on itself, resulting in a structure called a double helix. RNA molecules can be divided into three types, each with a specific function:
  • Transfer RNA (tRNA)
  • Messenger RNA (mRNA)
  • Ribosomal RNA (rRNA)

Chemical nature

A biopolymer, or large biomolecule, nucleic acid is essential for all forms of life. Five carbon atoms make up nucleotides, as well as a nitrogenous base and a phosphate group. Nucleic acids are classified primarily as ribonucleic acid (RNA) and deoxyribonucleic acid (DNA). Polymers made from sugars are either RNA or DNA depending on whether it is ribose sugar or the ribose derivative deoxyribose sugar.

Biological role

Replication - DNA replication is the process that makes two identical copies of a single DNA molecule. Enzymes are involved in the replication. In this process, DNA helix strands unwind into templates or patterns that serve as templates for the synthesis of multiple new strands. An exact copy of the original DNA is created by synthesizing a complementary strand. Hereditary characteristics can therefore be passed from cell to cell.

Transcription - By using DNA, it is possible to synthesize RNA (mRNA). A replication process occurs by using DNA as a template. However, they differ in several ways. Transcribing works by assembling ribose nucleotides on uncoiled templates instead of deoxyribose nucleotides, and uracil (U) replaces thymine (T). DNA or RNA is always synthesized in a 5' - 3' direction. RNA polymerase is used to catalyze the process. mRNA is created by the transfer of genetic information from DNA. The RNA that is synthesized will detach from the DNA and move from the nucleus to the cytoplasm, where it will serve as a template for protein synthesis. After DNA synthesis, RNA returns to the double helix structure.

Translation - A protein is synthesized during this process. This process occurs with the attachment of mRNA to ribosome particles (RNA - protein complex) in the cell's cytoplasm. The mRNA then transmits the DNA message, which dictates the amino acid sequence for protein synthesis. As with DNA, the bases in mRNA are arranged in triplets, with each triplet code for a particular amino acid. Each triplet is referred to as a codon. The same amino acid can be represented by multiple codons. The amino acid methionine has 13 code AUG and glycine has 4 code GGU, GGC, GGA, GGG. The codons are expressed in mRNA by tRNA containing anticodons, which translate into amino acids. Hence, proteins are synthesized by repeating this process. Ribosomes release them after they have been synthesized.

Protein synthesis - Adding 20 amino acids a second to protein synthesis is a fast and efficient process. Unlike translation, transcription does not always follow the same direction. The reverse transcription of RNA into DNA (occurs in retroviruses) is known as reverse transcription. A codon specifies a single amino acid and a gene is a segment of DNA containing three nucleotides. Nucleotide triplets are arranged in this relationship with amino acids called genetic code.
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