DNA consists of long polymers of simple units called nucleotides, with backbones made of sugars and phosphate groups joined by ester bonds. These strands run in opposite directions to each other and are therefore anti-parallel. Attached to each sugar is of types of molecules called bases. It is the sequence of these bases along the backbone that encodes information. This information is read using the genetic code, which specifies the sequence of the amino acids within proteins. The code is read by copying stretches of DNA in to the related nucleic acid RNA, in a technique called transcription.
Deoxyribonucleic acid , or DNA, is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms (with the exception of RNA viruses). The main role of DNA molecules is the long-term storage of information. DNA is often compared to a set of blueprints, like a recipe or a code, since it contains the instructions needed to construct other parts of cells, such as proteins and RNA molecules. The DNA segments that over this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in regulating the use of this genetic information.
- Within cells, DNA is organized in to long structures called chromosomes. These chromosomes are duplicated before cells divide, in a technique called DNA replication. Eukaryotic organisms (animals, plants, fungi, and protists) store most of their DNA inside the cell nucleus as well as a number of their DNA in organelles, such as mitochondria or chloroplasts.[1] In contrast, prokaryotes (bacteria and archaea) store their DNA only in the cytoplasm. Within the chromosomes, chromatin proteins such as histones compact and organize DNA. These compact structures guide the interactions between DNA and other proteins, helping control which parts of the DNA are transcribed
