Introduction


Nucleic acids are polymers of ribonucleotides or deoxyribonucleotides and are associated with the nucleus of a cell. DNA and RNA are the important nucleic acids found in the cells.

Structure


A nucleotide contains a nitrogenous base, phosphate group and sugar. An organic molecule containing a nitrogenous base called purine or pyrimidine is present in nucleotide. Purines are adenine or guanine and pyrimidines are cytosine, thymine or Uracil. Depending on the number of phosphate groups present in nucleotides, they are known as nucleotide monophosphates, diphosphates or triphosphates.

Types of nucleic acids


There are two types of nucleic acids, deoxyribonucleic acid and ribonucleic acid.

DNA


DNA is a very long thread like molecule made up of a very large number of deoxyribonucleotides joined together. DNA is a linear double stranded polymer made up of deoxyribonucleotides. Deoxyribonucleotide is made up of a sugar called deoxyribose, a nitrogenous base and a phosphate group. DNA is located in the nucleus. Nucleotides are joined together by a phosphodiester bond in a condensation reaction. Double helix is formed when two strands are joined together by hydrogen bonds. Double helix is anti parallel. Both the stands run in opposite direction and are parallel to each other.

RNA


RNA is a linear polymer in which nucleotides are linked together by means of phosphodiester bridges. It does not form a double helix like DNA. There are three different types of RNA: mRNA, tRNA and rRNA. Most RNA molecules usually have secondary structure, consisting of stem and loop domains. mRNA is linear in structure, variable in size, has a poly A tail and acts as a template for protein synthesis. tRNA has a clover leaf structure. rRNA is large in size and is associated with protein. All the three types of RNA are associated in the production of a protein.