Join point.
The site where two DNA molecules are connected. Commonly used to describe the junction at the site of a DNA rearrangement such as an inversion mutation.

Junction fragments
DNA fragments adjacent to a particular region of DNA. For example, DNA sequences adjacent to a transposon insertion or DNA sequences adjacent to a DNA fragment that can be detected with a specific probe.

Junk DNA
Regions of DNA that do not encode functional proteins or RNAs and do not function as regulatory sites. Most eukaryotic genomes that have been characterized contain substantial amounts of junk DNA but most prokaryotic genomes that have been characterized contain less than 15% junk DNA. (However, there are exceptions -- for example, the bacterium Mycobacterium leprae has substantial amounts of junk DNA.