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Repeated sequences (also known as repetitive elements, repeating units or repeats) are short or long patterns that occur in multiple copies throughout the genome.In many organisms, a significant fraction of the genomic DNA is repetitive, with over two-thirds of the sequence consisting of repetitive elements in humans. [1]
The repeats, or duplications, are typically 10–300 kb in length, and bear greater than 95% sequence identity. Though rare in most mammals, LCRs comprise a large portion of the human genome owing to a significant expansion during primate evolution. [1] In humans, chromosomes Y and 22 have the greatest proportion of SDs: 50.4% and 11.9% ...
A tract of repetitive DNA in which a motif of a few base pairs is tandemly repeated numerous times (e.g. 5 to 50 times) is referred to as microsatellite DNA. Thus direct repeat tandem sequences are a form of microsattelite DNA. The process of DNA mismatch repair plays a prominent role in the formation of direct trinucleotide repeat expansions. [2]
In genetics, tandem repeats occur in DNA when a pattern of one or more nucleotides is repeated and the repetitions are directly adjacent to each other, e.g. ATTCG ATTCG ATTCG, in which the sequence ATTCG is repeated three times. [1] Several protein domains also form tandem repeats within their amino acid primary structure, such as armadillo ...
Termination at a specific locus, when it occurs, involves the interaction between two components: (1) a termination site sequence in the DNA, and (2) a protein which binds to this sequence to physically stop DNA replication. In various bacterial species, this is named the DNA replication terminus site-binding protein, or Ter protein.
In addition to occurring during DNA replication, trinucleotide repeat expansion can also occur during DNA repair. [4] When a DNA trinucleotide repeat sequence is damaged, it may be repaired by processes such as homologous recombination, non-homologous end joining, mismatch repair or base excision repair.
During normal DNA replication, the polymerase on the lagging strand is required to unclamp and re-clamp the replication region continuously. [24] When small scale repeats in the DNA sequence exist already, the polymerase can be 'confused' when it re-clamps to continue replication and instead of clamping to the correct base pairs, it may shift a ...
These repeated DNA sequences often range from a pair of nucleotides to a whole gene, while the proximity of the repeat sequences varies between widely dispersed and simple tandem arrays. [3] The short tandem repeat sequences may exist as just a few copies in a small region to thousands of copies dispersed all over the genome of most eukaryotes. [4]