Deoxyribonucleic acid (DNA) is an organic chemical that contains genetic information and instructions for protein synthesis. It is found in most cells of every organism. DNA is a key part of reproduction in which genetic heredity occurs through the passing down of DNA from parent or parents to their offspring's. Genes are made of deoxyribonucleic acid (DNA), a long molecule composed of building blocks called nucleotides. Each nucleotide is built around one of four different subunits called bases. Mutation is replacement of nitrogen base with another in one or both the strands or addition or deletion of a base pair in a DNA molecule. The substances which can induce mutations are collectively known as mutagens. These can be chemicals, radiations or viruses. Genetic disorders can be caused by the mutation of one or more genes. Cancer is another disease caused by the mutation in genes that regulate the cell cycle.