Nucleic acids present in all living cells in combination with proteins to form conjugated protein called nucleoprotein. Nucleic acids are polymers of specific nucleotides. The nucleic acids are of two different types: deoxyribonucleic acid (DNA), Ribonucleic acid (RNA). DNA serves as the master copy for most information in the cell. RNA transforms information from DNA to the rest of the cell. The transfer of genetic information takes place in three processes such as replication, transcription and translation. This chapter also deals with recombinant DNA technology, polymerase chain reaction, Southern, northern and western blotting techniques, plasmids and libraries. A mutation is a permanent change in the DNA sequence of a gene. Mutations in a gene’s DNA sequence can alter the amino acid sequence of the protein encoded by the gene. There are many type of mutation: Frame shift mutation, Missense mutation, neutral mutation, nonsense mutation, point mutation and silent mutation.