Final answer:
Transposons are DNA segments that move within a genome through transposase-mediated mechanisms, either cut-and-paste or replicative, contributing to genetic diversity but also regulated to prevent potential harmful effects.
Step-by-step explanation:
DNA-Only Transposons and Transposase Function
DNA-only transposons are segments of DNA that move to different parts of the genome via an enzyme called transposase. The transposase enzyme is integral to the process of transposition, which can occur via a cut-and-paste or replicative mechanism. In the cut-and-paste model, transposase makes a staggered cut in the DNA to excise the transposon and then facilitates its insertion into a new target DNA site by nicking and ligating the DNA ends.
In this process, the 3'OH ends of the transposon are joined to the 5'OH of the insertion site, and the resulting gaps are filled in by DNA replication, creating direct repeats of host cell genomic DNA. During replicative transposition, the transposon is not completely excised but rather uses a hydrolytic attack to integrate a copy while keeping the original in place; a cointegrate structure forms, which then undergoes resolution through recombination.
Transposons are known to contribute to genetic diversity and can potentially cause mutations or changes in gene expression, hence their activity and insertion sites are tightly regulated in organisms. While sometimes considered 'junk DNA', transposons hold evolutionary and functional significance that has shaped genomes over time.