Regarding #8: 99% of what’s currently considered junk DNA is indeed junk. While we still discover new regulatory functions for a tiny fraction of intronic and intergenic sequences, we do not rely on lack of evidence of function to conclude that most of it is junk. There is positive evidence that only a small fraction of the human genome can be under selective pressure for its sequence.
About 50% of junk DNA are repeat sequences derived from transposons and viruses which are now inactive. A tiny fraction of these have taken on regulatory functions as the genes around them have adapted to their insertion. Most are still junk. There isn’t strong selective pressure to shrink genome sizes and plenty of mechanisms that increase it. There are species of Allium (garlic and onion families) with genome sizes ranging from about 2x to 8x the size of the human genome.
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Regarding #8: 99% of what’s currently considered junk DNA is indeed junk. While we still discover new regulatory functions for a tiny fraction of intronic and intergenic sequences, we do not rely on lack of evidence of function to conclude that most of it is junk. There is positive evidence that only a small fraction of the human genome can be under selective pressure for its sequence.
About 50% of junk DNA are repeat sequences derived from transposons and viruses which are now inactive. A tiny fraction of these have taken on regulatory functions as the genes around them have adapted to their insertion. Most are still junk. There isn’t strong selective pressure to shrink genome sizes and plenty of mechanisms that increase it. There are species of Allium (garlic and onion families) with genome sizes ranging from about 2x to 8x the size of the human genome.