My definition of tissue and DNA is perfectly all right.
The answer to my question is: Scientists have no idea what 98% of the Human Genome is for. They think that 20% is definitely junk, "pseudogenes" and most of the rest has no discernible purpose. But my guess is the bulk of the Human genome does have a purpose and their ignorance of its function merely reflects their general ignorance of the workings of the Human organism, particularly the brain and nervous system. What a shame it is they just can't say "We don't know" instead of "it's all a load of rubbish, there's nothing to know". So when they use matching DNA sequences to justify the inheritability of psychological traits, they may not be able to link those sequences to physical attributes, but you could ask, is that Junk DNA or what is it?