Final answer:
Non-LTR retrotransposons, like SINEs, move within the genome using Insertion Target-Site Primed Retrotransposition. They lack long terminal repeats but have untranslated regions flanking their open reading frames. Non-LTR retrotransposons rely on L1 LINE retrotransposons for enzyme activities needed for retrotransposition.
Step-by-step explanation:
Non-LTR retrotransposons, such as SINEs, are a type of transposable element that move within the genome through a process called Insertion Target-Site Primed Retrotransposition. Unlike LTR retrotransposons, non-LTR retrotransposons do not have long terminal repeats (LTRs). Instead, they contain 5' and 3' untranslated regions (UTRs) flanking their open reading frames (ORFs).
Non-LTR retrotransposons require the activity of L1 LINE retrotransposons to transpose. L1 LINE retrotransposons encode the enzymatic activities necessary for retrotransposition, including reverse transcriptase, RNAse H, and integrase. When a non-LTR SINE retrotransposon, such as the Alu element, needs to transpose, it relies on the concurrent activity of L1 LINE retrotransposons to provide the required enzyme functions.
In extrachromosomally primed retrotransposition, a circular reverse transcript of the retrotransposon integrates into a genomic insertion site. Reverse transcriptase creates a cDNA copy of the retrotransposon, which is then circularized by integrase/endonuclease. This circularized ribonucleoprotein, resembling an intasome, integrates into the genomic DNA at a different location.