Table 2.

Examples of TEs having functions that benefit their hosts

New function	Examples
Insertions with regulatory functions	More than 20 examples of insertions into regulatory regions of genes (12, 38, 39)
“Molecular domestication”	P element tandem repeats in D. obscura group may provide a new host gene function (89)
Source of new introns	Introns and twintrons in Euglena gracilis plastids (24)
Replacement of normal host functions	Repair of damaged chromosome ends by HET-A and TART in Drosophila (92, 93)
A role in host cell repair mechanisms	Endogenous retroelements associated with repair of DSBs in yeast (94, 95)
Mediation of concerted evolution	P element-mediated changes in subtelomeric repeat numbers in D. melanogaster (96)
Possible functions of heterochromatic TE clusters	Developmentally programmed changes in DNA content; expression of heterochromatically embedded loci; genomic housekeeping functions (25)

DSB, double-strand chromosome break.