For starters, junk DNA is a fuzzy term. I would never include regulatory regions or introns in junk DNA, just non-coding. To me, junk are tranposons and friends

For starters, junk DNA is a fuzzy term. I would never include regulatory regions or introns in junk DNA, just non-coding. To me, junk are tranposons and friends, or pseudogenes: they rarely have any purpose, and sometime they cause troubles.