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Satellite DNA

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Satellite DNA is a fraction of DNA consisting of millions of short, tandemly repeating, non-coding DNA. These sequences produce "sattelite" bands when DNA is centrifuged to separate it into fractions with different densities.[1] The DNA of constitutive heterochromatin mostly consists of satellite DNA.[2] Every normal centromere is located on satellite DNA.[1]

Satellite DNA often have unusual properties such as they can be identified as a separate peak in a density gradient analysis of DNA which came to be the reason given for its name.[3]

The primary structure of repeating units of satellite DNAs has been established in a number of organisms although the study of its chemical structure did not reveal any known function: satellite DNAs do not determine the structure of any protein.[4]

Types of satellite DNA

Some types of satellite DNA in humans are[2]:

Type Size of repeat unit (bp) Sequence of repeat unit Location
α (alphoid DNA) 170 [5] or 171 [2] Centromeric heterochromatin of all chromosomes
β (Sau3A family) 68 Centromeric heterochromatin of 1, 9, 13, 14, 15, 21, 22 and Y
Satellite 1 25-48 (AT-rich) Centromeres and other regions in heterochromatin of most chromosomes
Satellite 2 5 diverged forms of ATTCC/GGAAT Most, possibly all, chromosomes
Satellite 3 5 ATTCC/GGAAT Most chromosomes

History

The term satellite DNA was used by the first time by Saul Kit in 1961 in a density gradient ultracentrifugation analysis of DNA from some animals.[4] In his work, Kit carried out experiments in DNA from adult mouse tissues, three tumors, mouse tissue culture cells, and from three different tissues of the monkey, the guinea-pig, and the alligator.[6]

References

  1. 1.0 1.1 Wells, Jonathan (2011). The Myth of Junk DNA. Seattle: Discovery Institute Press. ISBN 978-1-9365990-0-4. 
  2. 2.0 2.1 2.2 Strachan, Tom; Read, Andrew (2011). Human Molecular Genetics (4th ed.). New York: Garland Science. ISBN 978-0-8153-4149-9. 
  3. Krebs, Jocelyn E.; Goldstein, Elliott S.; Kilpatrick, Stephen E. (2010). Lewin's Essential Genes (2nd ed.). Sudbury, Massachusetts: Jones and Bartlett. p. 123. ISBN 978-0-7637-5915-5. 
  4. 4.0 4.1 Beridze, Thengiz (1986). Satellite DNA. Berlin: Springer-Verlag. p. 1. ISBN 978-3-642-70773-5. 
  5. Tyler-Smith, Chris; Brown, William R. A. (1987). "Structure of the major block of alphoid satellite DNA on the human Y chromosome". Journal of Molecular Biology 195 (3): 457–470. PMID 2821279. 
  6. Kit, Saul (December 1961). "Equilibrium sedimentation in density gradient of DNA preparations from animal tissues". Journal of Molecular Biology 3 (6): 711-716. ISSN 0022-2836.