What is satellite dna

The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved. Highly repetitive, non-transcribed DNA regions in eukaryotic chromosomes that have a different sedimentatin coefficient than other nuclear DNA. Satellite DNA contains many thousands to over 100,000 tandem—not inverted—repeats of a short basic motif or repeat unit—commonly 100 to 300 base pairs which occur at a few loci on the genome unit and differ from ‘main band’ DNA Because unequal crossovers seem to be the prevalent mechanism producing copy-number variation in satellite DNA (Smith, 1976; Dover et al., 1982), recombination may counteract molecular parasitism in an entirely different way, by generating variation in copy number upon which either drift or selection can then act. The hypothesis that centromeric and telomeric locations confer greater evolutionary longevity on satellite DNA and permit its spread among the chromosomes (Charlesworth et al., 1986) could be tested more fully with knowledge of the chromosomal locations and the variability in abundance, within and between species, of satellite DNA families from a group of organisms whose phylogeny has been accurately reconstructed.

We all know that Eukaryotic genomes are composed of a large number of different classes of the repetitive sequences of the DNA. It is found either in an arranged tandem or in a dispersed manner. Satellite DNA consists of a repeated sequence. This region usually encodes for the proteins and some enzymes. Satellite DNA refers to the phenomenon where the repetitions of short sequences of the DNA tends to produce a frequency difference in the bases adenine, cytosine, guanine, and thymine, and thus it has a different density from the bulk DNA and it forms a second or satellite band when the genomic DNA is separated in a density gradient. Sequences that have a greater ratio of adenine and Thymine displays as a lower density whereas the greater ratio of Guanine and Cytosine displays a higher density than the bulk genomic DNA Satellite DNA is present in the heterochromatin region of the chromosomes. Or in the tightly packed regions of the chromosomes, such as centromeres or telomeres. Sometimes the euchromatin region, which is also known as an active region of the genome contains the Satellite DNA. Though satellite DNA has been known as non-coding, as it does not encode proteins. Recent evidence ensures that some of the satellite DNA undergoes transcription. The short tandem repeats are called microsatellites or simple sequence repeats, whereas the long tandem repeats are called minisatellites or variable number tandem repeats. The regions that are present between the two simple s...

This article is about the DNA sequence. For small orbiting spacecraft, see A microsatellite is a tract of repetitive short tandem repeats ( STRs) by simple sequence repeats ( SSRs) by plant geneticists. Microsatellites and their longer cousins, the They are widely used for History [ ] Although the first microsatellite was characterised in 1984 at the Structures, locations, and functions [ ] A microsatellite is a tract of tandemly repeated (i.e. adjacent) DNA motifs that range in length from one to six or up to ten nucleotides (the exact definition and delineation to the longer minisatellites varies from author to author), Microsatellites in non-coding regions may not have any specific function, and therefore might not be [ citation needed] They are thus classified as [ citation needed] Mutation mechanisms and mutation rates [ ] Unlike One proposed cause of such length changes is replication slippage, caused by mismatches between DNA strands while being replicated during meiosis. Another possible cause of microsatellite mutations are point mutations, where only one nucleotide is incorrectly copied during replication. A study comparing human and primate genomes found that most changes in repeat number in short microsatellites appear due to point mutations rather than slippage. Microsatellite mutation rates [ ] Direct estimates of microsatellite mutation rates have been made in numerous organisms, from insects to humans. In the Schistocerca gregaria, the microsatellite mutati...