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DNA: Deoxyribonucleic acid (DNA) is a molecule encoding the genetic instructions used in the development and functioning of all known living organisms and many viruses. Along with RNA and proteins, DNA is one of the three major macromolecules that are essential for all known forms of life. Genetic information is encoded as a sequence of nucleotides (guanine, adenine, thymine, and cytosine) recorded using the letters G, A, T, and C. Most DNA molecules are double-stranded helices, consisting of two long polymers of simple units called nucleotides, molecules with backbones made of alternating sugars (deoxyribose) and phosphate groups (related to phosphoric acid), with the nucleobases (G, A, T, C) attached to the sugars. During protein synthesis, DNA is transcribed into RNA and then translated to produce proteins. But an error in a single letter in that sequence may damage the entire structure. The leukemia observed in children appears because one of the letters in the DNA is incorrect. The reason for diseases such as cancer appearing or subsequent generations being deformed as a result of the radiation leakage in Chernobyl of the atom bomb dropped over Hiroshima is harmful effects of this kind caused by mutations in people’s bodies. -------------------------------------- What are mutations ? A gene mutation is defined as an alteration in the sequence ofnucleotides in DNA. This change can affect a single nucleotide pair orlarger gene segments of a chromosome. DNA consists of a polymer of nucleotides joined together. Altering nucleotide sequences most often results in nonfunctioning proteins. Mutations cause changes in the genetic code that lead to genetic variation and the potential to develop disease. Types of mutations:below