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Direct repeat
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<h2 id="types">Types</h2> <p>There are several types of repeated sequences: </p> <ul><li>Interspersed (or dispersed) DNA repeats (interspersed repetitive sequences) are copies of <a href="/facts/Transposable_elements/WbVMhuWR">transposable elements</a> interspersed throughout the genome.</li> <li>Flanking (or terminal) repeats (terminal repeat sequences) are sequences that are repeated on both ends of a sequence, for example, the <a href="/facts/Long_terminal_repeat/LV5ADTam">long terminal repeats</a> (LTRs) on <a href="/facts/Retroviruses/GWAx3C3o">retroviruses</a>. Direct terminal repeats are in the same direction and inverted terminal repeats are opposite to each other in direction.</li> <li><a href="/facts/Tandem_repeats/V40yCKFJ">Tandem repeats</a> (tandem repeat sequences) are repeated copies which lie adjacent to each other. These can also be direct or <a href="/facts/Inverted_repeats/81kE3X3s">inverted repeats</a>. The <a href="/facts/Ribosomal_RNA/zy5FxddY">ribosomal RNA</a> and <a href="/facts/Transfer_RNA/pR9T5XSl">transfer RNA</a> genes belong to the class of middle repetitive DNA.</li></ul> <h3>Microsatellite DNA</h3> <p>A tract of <a href="/facts/Repeated_sequence_(DNA)/hPosWry7">repetitive DNA</a> in which a motif of a few base pairs is tandemly repeated numerous times (e.g. 5 to 50 times) is referred to as <a href="/facts/Microsatellite/SwfHbeXG">microsatellite</a> DNA. Thus direct repeat tandem sequences are a form of microsattelite DNA. The process of <a href="/facts/DNA_mismatch_repair/qHaxxs6C">DNA mismatch repair</a> plays a prominent role in the formation of direct trinucleotide repeat expansions.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a> Such repeat expansions underlie several neurological and developmental disorders in humans.<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> </p> <h2 id="homologous-recombination">Homologous recombination</h2> <p>In directly repeated sequences of the <a href="/facts/Tobacco/bTD4RUPQ">tobacco</a> plant <a href="/facts/Genome/31Sm08JT">genome</a>, <a href="/facts/DNA_damage_(naturally_occurring)/CjGTLKGl">DNA double-strand breaks</a> can be efficiently repaired by <a href="/facts/Homologous_recombination/WU0IIVVv">homologous recombination</a> between the repeated sequences.<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> </p> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/Inverted_repeat/81kE3X3s">Inverted repeat</a></li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Ussery, David W.; Wassenaar, Trudy; Borini, Stefano (2009). "Word Frequencies and Repeats §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. doi:10.1007/978-1-84800-255-5_8. ISBN 978-1-84800-254-8. <a href="978-1-84800-254-8" target="_blank">978-1-84800-254-8</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Ussery, David W.; Wassenaar, Trudy; Borini, Stefano (2009). "Word Frequencies and Repeats §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. doi:10.1007/978-1-84800-255-5_8. ISBN 978-1-84800-254-8. <a href="978-1-84800-254-8" target="_blank">978-1-84800-254-8</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Ussery, David W.; Wassenaar, Trudy; Borini, Stefano (2009). "Word Frequencies and Repeats §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. doi:10.1007/978-1-84800-255-5_8. ISBN 978-1-84800-254-8. <a href="978-1-84800-254-8" target="_blank">978-1-84800-254-8</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>Richard, G. F. (2021). "The Startling Role of Mismatch Repair in Trinucleotide Repeat Expansions". Cells. 10 (5): 1019. doi:10.3390/cells10051019. PMC 8145212. PMID 33925919. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8145212" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8145212</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Richard, G. F. (2021). "The Startling Role of Mismatch Repair in Trinucleotide Repeat Expansions". Cells. 10 (5): 1019. doi:10.3390/cells10051019. PMC 8145212. PMID 33925919. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8145212" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8145212</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>Siebert R, Puchta H (May 2002). "Efficient repair of genomic double-strand breaks by homologous recombination between directly repeated sequences in the plant genome". Plant Cell. 14 (5): 1121–31. doi:10.1105/tpc.001727. PMC 150611. PMID 12034901. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC150611" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC150611</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> </ol>