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DNA, or deoxyribonucleic acid, is the hereditary material found in all living organisms and many viruses. It contains the genetic instructions necessary for growth, development, reproduction, and maintenance of life. DNA is composed of two long strands forming a double helix, with each strand made up of repeating units called nucleotides. Each nucleotide consists of three components: a sugar molecule (deoxyribose), a phosphate group, and a nitrogenous base.

The four types of nitrogenous bases in DNA are adenine, thymine, cytosine, and guanine. These bases pair specifically via hydrogen bonds, with adenine pairing with thymine and cytosine pairing with guanine, forming the rungs of the DNA ladder. This base pairing underpins DNA's ability to replicate accurately during cell division.

DNA's structure allows it to store vast amounts of genetic information within the sequence of its bases. This information is transcribed into RNA, which then guides protein synthesis, the process by which cells produce the proteins necessary for life. The entire human genome contains approximately 3 billion base pairs distributed across 23 pairs of chromosomes.

DNA was discovered in 1869 by Friedrich Miescher and later identified as the genetic material in the 20th century through experiments by scientists such as Watson, Crick, Franklin, and Wilkins. It plays a crucial role in genetics, heredity, and biotechnology, serving as the blueprint for the diversity of life on Earth. Advances in DNA research have led to fields such as genetic engineering, forensic science, and personalized medicine.