Repeated sequence (DNA)

Repeated sequences (aka. repetitive elements, or repeats) are patterns of nucleic acids (DNA or RNA) that occur in multiple copies throughout the genome. The functions and descriptions of these sequences are currently being characterized by scientists. Repetitive DNA was first detected because of its rapid reassociation kinetics.

Types

Main types

There are 3 major categories of repeated sequence or repeats:

• Terminal repeats
• Tandem repeats: copies which lie adjacent to each other, either directly or inverted
  • Satellite DNA - typically found in centromeres and heterochromatin
  • Minisatellite - repeat units from about 10 to 60 base pairs, found in many places in the genome, including the centromeres
  • Microsatellite - repeat units of less than 10 base pairs; this includes telomeres, which typically have 6 to 8 base pair repeat units
• Interspersed repeats (aka. interspersed nuclear elements)
  • Transposable elements
    • DNA transposons
    • retrotransposons
      • LTR-retrotranposons (HERVs)
      • non LTR-retrotranposons
        • SINEs (Short Interspersed Nuclear Elements)
        • LINEs (Long Interspersed Nuclear Elements)
        • SVAs

In primates, the majority of LINEs are LINE-1 and the majority of SINEs are Alu's. SVAs are hominoid specific.

In prokaryotes, CRISPR are arrays of alternating repeats and spacers.

Other types

Note: The following are covered in detail in "Computing for Comparative Microbial Genomics".^[1]

• Direct repeats
  • Global direct repeat
  • Local direct simple repeats
  • Local direct repeats
  • Local direct repeats with spacer
• Inverted repeats
  • Global inverted repeat
  • Local inverted repeat
  • Inverted repeat with spacer
  • Palindromic repeat
• Mirror and everted repeats

See also

• Eukaryotic chromosome fine structure
• Non-coding DNA
• Intergenic DNA

References

External links

• Function of Repetitive DNA
• DNA Repetitious Region at the US National Library of Medicine Medical Subject Headings (MeSH)