DNA (duo)

DNA, or deoxyribonucleic acid, is a molecule that carries the genetic instructions used in the growth, development, functioning and reproduction of all known living organisms and many viruses. DNA is a nucleic acid; alongside proteins and carbohydrates, nucleic acids are one of the three major macromolecules essential for all known forms of life.

DNA is a polymer made of repeating units called nucleotides. Each nucleotide is composed of three components: a deoxyribose sugar, a phosphate group, and a nitrogenous base. There are four different types of nitrogenous bases in DNA: adenine (A), guanine (G), cytosine (C), and thymine (T).

DNA typically exists as a double-stranded helix, with the two strands running anti-parallel to each other. The nitrogenous bases on each strand pair up according to specific rules: adenine (A) always pairs with thymine (T), and guanine (G) always pairs with cytosine (C). This specific pairing is known as complementary base pairing and is crucial for DNA replication and transcription. The two strands are held together by hydrogen bonds between the complementary base pairs.

DNA contains the genetic information necessary for the synthesis of proteins. This process occurs in two main steps: transcription and translation. During transcription, the DNA sequence is copied into a messenger RNA (mRNA) molecule. The mRNA then carries this genetic information to ribosomes, where it is translated into a sequence of amino acids, which folds to form a functional protein.

DNA is located within the cell's nucleus in eukaryotes and in the cytoplasm in prokaryotes. In eukaryotes, DNA is organized into structures called chromosomes, which are tightly coiled and compacted to fit within the nucleus. The structure and organization of DNA allows for efficient storage and replication of genetic information.

DNA replication is the process by which a DNA molecule is duplicated. This process is essential for cell division and ensures that each daughter cell receives a complete copy of the genetic material. DNA replication is a complex process involving several enzymes, including DNA polymerase, which synthesizes new DNA strands by adding nucleotides to the existing strand.

Mutations, or changes in the DNA sequence, can occur spontaneously or be induced by environmental factors such as radiation or chemicals. Some mutations can be harmful, leading to diseases or other genetic disorders, while others may be neutral or even beneficial. The study of DNA and genetics has revolutionized many fields, including medicine, agriculture, and forensics.