DNA

DNA, short for deoxyribonucleic acid, is the molecule that contains the genetic code of organisms. This includes animals, plants, protists, archaea and bacteria. It is made up of two polynucleotide chains in a double helix.^[1]

DNA is in each cell in the organism and tells cells what proteins to make. Mostly, these proteins are enzymes. DNA is inherited by children from their parents. This is why children share traits with their parents, such as skin, hair and eye color. The DNA in a person is a combination of the DNA from each of their parents.

Part of an organism's DNA is "non-coding DNA" sequences. They do not code for protein sequences. Some noncoding DNA is transcribed into non-coding RNA molecules, such as transfer RNA, ribosomal RNA, and regulatory RNAs.^[2] Other sequences are not transcribed at all, or give rise to RNA of unknown function. The amount of non-coding DNA varies greatly among species. For example, over 98% of the human genome is non-coding DNA,^[3] while only about 2% of a typical bacterial genome is non-coding DNA.

Viruses use either DNA or RNA to infect organisms.^[4] The genome replication of most DNA viruses takes place in the cell's nucleus, whereas RNA viruses usually replicate in the cytoplasm.

Inside eukaryotic cells, DNA is organized into chromosomes. Before cell division, more chromosomes are made in the process of DNA replication. Eukaryotic organisms like animals, plants, fungi and protists store most of their DNA inside the cell nucleus. But prokaryotes, like bacteria and archaea store their DNA only in the cytoplasm, in circular chromosomes. Inside eukaryotic chromosomes, chromatin proteins, such as histones, help to compact and organize DNA.^[5]

1. ↑ "Definition of DEOXYRIBONUCLEIC ACID". www.merriam-webster.com. Retrieved 2022-04-23.
2. ↑ Alberts, Bruce (2015). Molecular biology of the cell (Sixth ed.). New York, NY. ISBN 978-0-8153-4432-2. OCLC 887605755.{{cite book}}: CS1 maint: location missing publisher (link)
3. ↑ Elgar G. & Vavouri T. 2008. Tuning in to the signals: non-coding sequence conservation in vertebrate genomes. Trends Genet. 24 (7): 344–52. doi:10.1016/j.tig.2008.04.005
4. ↑ Van Etten JL, Lane LC, Dunigan DD (2010). "DNA viruses: the really big ones (giruses)". Annual Review of Microbiology. 64: 83–99. doi:10.1146/annurev.micro.112408.134338. ISSN 0066-4227. PMC 2936810. PMID 20690825.{{cite journal}}: CS1 maint: multiple names: authors list (link)
5. ↑ Alberts, Bruce (2002). Molecular biology of the cell. Alexander Johnson, Julian Lewis, Martin Raff, Keith Roberts, Peter Walter (4th ed.). New York: Garland Science. ISBN 0-8153-3218-1. OCLC 48122761.