Final answer:
Direct repeats are found at both ends of a transposable element after it inserts into a new location in the genome, common in both prokaryotic and eukaryotic transposons. While specifics can vary, such as non-LTR retrotransposons like LINES not having LTRs, the formation of direct repeats upon insertion is a typical feature of transposable elements.
Step-by-step explanation:
Direct repeats, also known as target-site duplications, are sequences that flank a transposable element at both the 5' and 3' ends after the element has inserted into a new location in the genome. In prokaryotic and eukaryotic organisms, these transposons move around within the genome and can cause duplication of short sequences of DNA at their target insertion sites. For instance, when the transposase enzyme of a DNA transposon excises the element to insert it into a new site, it creates a staggered cut in the host DNA. When the transposon is ligated into the new site, the single-stranded gaps are filled in, thereby creating direct repeats of the target DNA sequence on both ends of the transposon.
However, it is important to note that not all types of transposable elements generate direct repeats. For instance, non-LTR retrotransposons like LINES (Long Interspersed Nuclear Elements) do not possess long terminal repeats (LTRs) but still generate target-site direct repeats flanking the inserted element. Examples such as Ac and Ds elements in plants show inverted repeats at their ends, but these too are flanked by direct repeats at the insertion site following transposition.