Introduction to Nucleic Acids, Biology tutorial


Any of the group of complex compounds comprising of linear chains of monomeric nucleotides whereby each and every monomeric unit is comprised of phosphoric acid, sugar and nitrogenous base and engaged in the preservation, replication and expression of the hereditary information in all living cell.

Types of Nucleic Acids:

1) Ribonucleic Acid:

Ribonucleic acid or RNA is a nucleic acid polymer comprising of nucleotide monomers that plays some significant roles in the processes of transcribing genetic information from deoxyribonucleic acid (DNA) into the proteins. RNA acts as a messenger among DNA and the protein synthesis complexes termed as ribosomes, forms very important parts of ribosomes and serves as a necessary carrier molecule for amino acids to be employed in the protein synthesis.

2) Deoxyribonucleic Acid:

 Deoxyribonucleic acid is a nucleic acid which comprises of the genetic instructions employed in the growth and functioning of all known living organisms. The major role of DNA molecules is the long-term storage of information and DNA is frequently compared to a set of blueprints. It includes the instructions required to construct other components of cells, like proteins and RNA molecules. The DNA segments which carry this genetic information are termed as genes; however other DNA sequences encompass structural purposes, or are engaged in regulating the utilization of this genetic information.

DNA is building up of four kinds of bases namely cytosine, thymine, guanine and adenine that are linked altogether to prepare a chain. The bases are joined to one other in this chain through a sugar-phosphate backbone. Two of these chains then coil around one other, making the DNA double helix.

Nucleic Acid Structure:

Nucleotides are the fundamental building blocks of the nucleic acids. Each and every nucleotide is a monomer of nucleic acid and comprises of three parts:

  • A pentose sugar 
  • One or more phosphate groups 
  • One of five cyclic nitrogenous bases

Phosphate-Sugar Backbone:

Nucleotides are linked altogether through covalent bonds among phosphate of one nucleotide and sugar of next. Such linked monomers become the phosphate-sugar backbone of the nucleic acids. Nitrogenous bases expand from this phosphate-sugar backbone similar to teeth of a comb.

The Nucleic Acid Ladder:

Hydrogen bonds form among particular bases of two nucleic acid chains, making a stable, double-stranded DNA molecule that looks similar to a ladder.

Three H-bonds form among bases cytosine (C) and guanine (G) that always pair up altogether among the two nucleic acid chains. Two H bonds form among adenine (A) and thymine (T) in DNA or adenine and uracil (U) in the RNA molecules.

The structure is similar to a ladder, with the two deoxyribose-phosphate chains as side rails and the base pairs, linked through hydrogen bonds, making the rungs.

Organization of Nucleotides in the Nucleic Acids:

The manufacture of a nucleic acid is an anabolic polymerization procedure. Anabolic reactions manufacture bigger molecules. Polymerization is the procedure of taking nucleotide monomers and putting them altogether into polymers (big molecules composed of numerous monomers).

Such three-phosphate nucleotide building blocks of the DNA bring their own energy for polymerization in their phosphate bonds. If the triphosphate bond of the nucleotide is broken, it gives the energy needed add other nucleotide to the growing nucleic acid.

Chemical Structure:

The word 'nucleic acid' is the generic name for a family of biopolymers, termed for their role in the cell nucleus. The monomers from which nucleic acids are made are termed as nucleotides.

Each and every nucleotide comprises of three components: a nitrogenous heterocyclic base that is either a purine or a pyrimidine; a pentose sugar; and a phosphate group. The types of Nucleic acid vary in the structure of the sugar in their nucleotides - DNA comprises of 2-deoxyribose whereas RNA comprises of ribose (where the single difference is the presence of a hydroxyl group). As well the nitrogenous bases found in the two nucleic acid kinds are different: adenine, cytosine and guanine are found in both RNA and DNA, whereas thymine only takes place in DNA and uracil only takes place in RNA. Other unusual nucleic acid bases can take place, for instance inosine in strands of the mature transfer RNA.

Nucleic acids are generally either single-stranded or double-stranded; however structures having three or more strands can form. A double-stranded nucleic acid comprises of two single-stranded nucleic acids held altogether through hydrogen bonds, like in the DNA double helix. In contrast, RNA is generally single-stranded however any given strand might fold back on itself to form secondary structure as in tRNA and rRNA. In cells, DNA is generally double-stranded, although several viruses encompass single-stranded DNA as their genome. Retroviruses encompass single-stranded RNA as their genome.

The phosphates and sugars in nucleic acids are joined to one other in an alternating chain, linked through shared oxygen making a phosphodiester bond. In usual nomenclature, the carbons to which the phosphate groups join are the 3' end and the 5' end carbons of the sugar. This provides nucleic acids polarity.

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