satellite DNA
Introduction
When genomic DNA is mechanically broken into short fragments of ds DNA about 1000 base pairs long, & the fragments are denatured to produce single-stranded DNA. About 70% of the DNA renatures slowly, but 30% anneals much more quickly. The most rapidly annealing DNA strands consist of long tandem repeats. These repeats may be composed of 1 or two nucleotides, but more typically consist of variants of a short sequence organized into a repeat of a few hundred nucleotides. These tandem repeats of simple sequence are called satellite DNA because the first DNA of this type to be discovered had an unusual ratio of nucleotides that made it possible to separate them by density-gradient centrifugation from the bulk of cellular DNA as a microcomponent or 'satellite'. Satellite DNA sequences are usually not transcribed & are located most often in the heterochromatin associated with the centromeric regions of chromosomes. When 2 homologous mitotic chromosomes of any human are compared, some of the satellite sequences are usually found arranged in a different manner on the 2 chromosomes. No function has been found for satellite DNA.
More general terms
References
- ↑ Molecular Biology of the Cell, 3rd ed. Alberts, Bray, Lewis, Raff, Roberts & Watson (eds) Garland Publishing, New York 1994, pg 391