Satellite DNA

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. The DNA of constitutive heterochromatin mostly consists of satellite DNA. Every normal centromere is located on satellite DNA.

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.

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.

Types of satellite DNA
Some types of satellite DNA in humans are :

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. 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.