DNA

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Deoxyribonucleic acid (DNA) is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms and some viruses. The main role of DNA molecules is the long-term storage of information.

DNA is often compared to a set of blueprints or a recipe, or a code, since it contains the instructions needed to construct other components of cells, such as proteins and RNA molecules. The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in regulating the use of this genetic information.

For lessons on the topic of DNA, follow this link.

Chemically, DNA consists of two long polymers of simple units called nucleotides, with backbones made of sugars and phosphate groups joined by ester bonds. These two strands run in opposite directions to each other and are therefore anti-parallel. Attached to each sugar is one of four types of molecules called bases. It is the sequence of these four 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 into the related nucleic acid RNA, in a process called transcription.

Within cells, DNA is organized into long structures called chromosomes. These chromosomes are duplicated before cells divide, in a process called DNA replication. Eukaryotic organisms (animals, plants, fungi, and protists) store most of their DNA inside the cell nucleus and some 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.[1]

References

  1. Russell, Peter (2001). iGenetics. New York: Benjamin Cummings. ISBN 0-805-34553-1.
  2. Saenger, Wolfram (1984). Principles of Nucleic Acid Structure. New York: Springer-Verlag. ISBN 0387907629.
  3. Alberts, Bruce; Alexander Johnson, Julian Lewis, Martin Raff, Keith Roberts, and Peter Walters (2002). Molecular Biology of the Cell; Fourth Edition. New York and London: Garland Science. ISBN 0-8153-3218-1. OCLC 145080076 48122761 57023651 69932405.
  4. Butler, John M. (2001). Forensic DNA Typing. Elsevier. ISBN 978-0-12-147951-0. OCLC 223032110 45406517. pp. 14–15.
  5. Mandelkern M, Elias J, Eden D, Crothers D (1981). "The dimensions of DNA in solution". J Mol Biol 152 (1): 153–61. doi:10.1016/0022-2836(81)90099-1. PMID 7338906.

Further reading

  • Calladine, Chris R.; Drew, Horace R.; Luisi, Ben F. and Travers, Andrew A. (2003). Understanding DNA: the molecule & how it works. Amsterdam: Elsevier Academic Press. ISBN 0-12-155089-3.
  • Dennis, Carina; Julie Clayton (2003). 50 years of DNA. Basingstoke: Palgrave Macmillan. ISBN 1-4039-1479-6.
  • Judson, Horace Freeland (1996). The eighth day of creation: makers of the revolution in biology. Plainview, N.Y: CSHL Press. ISBN 0-87969-478-5.
  • Olby, Robert C. (1994). The path to the double helix: the discovery of DNA. New York: Dover Publications. ISBN 0-486-68117-3., first published in October 1974 by MacMillan, with foreword by *Francis Crick;the definitive DNA textbook,revised in 1994 with a 9 page postscript.
  • Olby, Robert C. (2009). Francis Crick: A Biography. Plainview, N.Y: Cold Spring Harbor Laboratory Press. ISBN 0-87969-798-9.

External links