Most of the genome is non protein coding. Some is functional, most simply is not functional in any way. It is just empty space. Rates of mutation in these regi

Most of the genome is non protein coding. Some is functional, most simply is not functional in any way. It is just empty space. Rates of mutation in these regions, and lack of conservation are hallmark clues which show that there isn't function in these regions. That doesn't mean totally useless, these non-functional regions provide the raw material for the creation of genes and functional elements. Its just that, right now, those regions aren't doing anything. No biologist calls it "junk DNA". That is just a simplified layman's term for media press releases.