Retrotransposon

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Retrotransposons are class I transposons that make up around 40% of the entire human genome[1].  They move from one genome to another by DNA being transcribed into RNA then back to DNA again, via the action of reverse transcriptase[2]. They are also known as 'jumping genes' as DNA is moved to a different position on the chromosome each time retrotransposition occurs[3].

There are 2 types of retrotransposons[4]:

  1. Long Terminal Receptors (LTRs) - these have structures similar to retroviruses
  2. Non-Long Terminal Receptors (non LTRs) - these are further divided into Long Interspersed Nuclear Elements (LINEs) and Short Interspersed Nuclear Elements (SINEs)

LINEs make up a majority of retrotransposons and around 17% of the human genome. LINE-1 (L1) is the largest LINE family. Functional L1 encodes the proteins:

LINEs are able to be used as markers in DNA fingerprinting due to the large diversity of them between individuals[5].

Retrotransposons are highly regulated starting from development in the womb. Most retrotransposons are inactive and repressed in adult somatic cells due to DNA methylation during development. DNA methylation prevents retrotransposons from being expressed in DNA[6].

References

  1. Kimball’s Biology Pages. Transposons: Mobile DNA. 2018 [cited 15/11/18]; Available From: http://www.biology-pages.info/T/Transposons.html
  2. Lander E, Linton L, Birren B, Nusbaum C, Zody M, Baldwin J et al. Initial sequencing and analysis of the human genome. Nature [Internet]. 2001
  3. Lander E, Linton L, Birren B, Nusbaum C, Zody M, Baldwin J et al. Initial sequencing and analysis of the human genome. Nature [Internet]. 2001
  4. The three Types of Retrotransposons [Internet]. Actforlibraries.org. 2018
  5. Kimball’s Biology Pages. Transposons: Mobile DNA. 2018 [cited 15/11/18]; Available From: http://www.biology-pages.info/T/Transposons.html
  6. Anwar S, Wulaningsih W, Lehmann U. Transposable elements in human cancer: causes and consequences of deregulation. International journal of molecular sciences. 2017 May 4;18(5):974. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5454887/
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