Editing Transposable element (section)

== Negative effects ==
Transposons have coexisted with [[eukaryote]]s for thousands of years and through their coexistence have become integrated in many organisms' genomes. Colloquially known as 'jumping genes', transposons can move within and between genomes allowing for this integration.

While there are many positive effects of transposons in their 
[[Host (biology)|host]] [[eukaryotic]] [[genome]]s,{{explain|date=November 2021}} there are some instances of mutagenic effects that TEs have on genomes leading to disease and malignant genetic alterations.<ref name=":0">Belancio VP, Hedges DJ, Deininger P (March 2008). "Mammalian non-LTR retrotransposons: for better or worse, in sickness and in health". ''Genome Research''. '''18''' (3): 343–58. [[Digital object identifier|doi]]:10.1101/gr.5558208. [[PubMed Identifier|PMID]] 18256243.</ref>

=== Mechanisms of mutagenesis ===
TEs are [[mutagen]]s and due to the contribution to the formation of new cis-regulatory DNA elements that are connected to many transcription factors that are found in living cells; TEs can undergo many evolutionary mutations and alterations. These are often the causes of genetic disease, and gives the potential lethal effects of ectopic expression.<ref name="Zhou 19359–19366"/>

TEs can damage the genome of their host cell in different ways:<ref name=":0" />

* A transposon or a retrotransposon that inserts itself into a functional gene can disable that gene.
* After a DNA transposon leaves a gene, the resulting gap may not be repaired correctly.
* Multiple copies of the same sequence, such as [[Alu sequence]]s, can hinder precise [[Chromosome|chromosomal]] pairing during [[mitosis]] and [[meiosis]], resulting in unequal [[Chromosomal crossover|crossovers]], one of the main reasons for chromosome duplication.

TEs use a number of different mechanisms to cause genetic instability and disease in their host genomes.

* Expression of disease-causing, damaging proteins that inhibit normal cellular function.
** Many TEs contain [[Promoter (genetics)|promoters]] which drive [[Transcription (genetics)|transcription]] of their own [[transposase]]. These promoters can cause aberrant expression of linked genes, causing disease or [[mutant]] [[phenotypes]].<ref>{{cite journal | vauthors = Dahlet T, Argüeso Lleida A, Al Adhami H, Dumas M, Bender A, Ngondo RP, Tanguy M, Vallet J, Auclair G, Bardet AF, Weber M | display-authors = 6 | title = Genome-wide analysis in the mouse embryo reveals the importance of DNA methylation for transcription integrity | journal = Nature Communications | volume = 11 | issue = 1 | pages = 3153 | date = June 2020 | pmid = 32561758 | pmc = 7305168 | doi = 10.1038/s41467-020-16919-w | bibcode = 2020NatCo..11.3153D }}</ref>