I probably should have clarified in the post but "Junk" DNA is a misnomer though still the most commonly used term for the part of the human genome (over 90% of it) that we don't know the uses for. The word "junk" isn't used in the sense that the DNA there is worthless and should be discarded. More like a junk drawer. There's a bunch of stuff over there that doesn't seem to belong to anything but we know that a lot of it probably does, so scientists keep testing around in there to see what goes where.