Direct repeat
Direct repeats are a type of genetic sequence that consists of two or more repeats of a specific sequence.[1] In other words, the direct repeats are nucleotide sequences present in multiple copies in the genome. Generally, a direct repeat occurs when a sequence is repeated with the same pattern downstream.[1] There is no inversion[clarification needed] and no reverse complement associated with a direct repeat. It may or may not have intervening nucleotides. The nucleotide sequence written in bold characters signifies the repeated sequence.
- 5´ TTACGnnnnnnTTACG 3´
- 3´ AATGCnnnnnnAATGC 5´
Linguistically, a typical direct repeat is comparable to saying "bye-bye".[1]
Types[]
There are several types of repeated sequences :
- Interspersed (or dispersed) DNA repeats (interspersed repetitive sequences) are copies of transposable elements interspersed throughout the genome.
- Flanking (or terminal) repeats (terminal repeat sequences) are sequences that are repeated on both ends of a sequence, for example, the long terminal repeats (LTRs) on retroviruses. Direct terminal repeats are in the same direction and inverted terminal repeats are opposite to each other in direction.
- Tandem repeats (tandem repeat sequences) are repeated copies which lie adjacent to each other. These can also be direct or inverted repeats.[citation needed] The ribosomal RNA and transfer RNA genes belong to the class of middle repetitive DNA.
See also[]
References[]
- ^ a b c Ussery, David W.; Wassenaar, Trudy; Borini, Stefano (2008-12-22). "Word Frequencies, Repeats, and Repeat-related Structures in Bacterial Genomes". Computing for Comparative Microbial Genomics: Bioinformatics for Microbiologists. Computational Biology. Vol. 8 (1 ed.). Springer. pp. 133–144. ISBN 978-1-84800-254-8.
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