DNAS

DNA, or deoxyribonucleic acid, stores the genetic information essential for growth, development, and functioning in most organisms and many viruses. In its common form DNA is a long, two-stranded polymer arranged as a double helix. Each strand consists of a sugar (deoxyribose), a phosphate backbone, and four bases: adenine, thymine, cytosine, and guanine. Bases pair A with T and C with G, enabling faithful replication and encoding information in base sequences.

DNA encodes genes and regulatory regions that control when and where genes are expressed. Genomes vary in size and organization. In eukaryotes, DNA is organized into linear chromosomes in the nucleus, with additional mitochondrial DNA. Prokaryotes typically have a single circular chromosome and may carry plasmids. The human genome comprises roughly 3 billion base pairs and tens of thousands of genes, with substantial noncoding regions.

DNA replication is semi-conservative, yielding two identical molecules from one. Transcription of DNA into RNA precedes translation into protein, though RNA also has regulatory roles. DNA repair systems correct damage, helping maintain genome integrity.

Genetic variation arises from mutations and recombination and underpins heredity and evolution. DNA is inherited across generations through various patterns of transmission. Modern methods analyze and manipulate DNA, including sequencing, amplification by PCR, cloning, and genome editing.

Applications span medicine, forensics, agriculture, and basic research. DNA sequencing informs diagnosis and personalized treatment; genetic engineering modifies organisms; comparative genomics reveals evolutionary relationships. Ethical, privacy, and biosafety considerations accompany these capabilities and guide policy and practice.