There is a large amount of DNA that does not ‘code’ for any known proteins, this DNA has been labelled ‘junk DNA’, reminiscent of garbage bags and messy basements carrying the leftovers of evolutionary dead-ends.
I don’t believe any of it. Nature is much too frugal to use 90% of our most precious molecules as a garbage dump, I think it is functional, and probably all of it rather than just some of it.
Stuff I fully expect to be present in the ‘junk’:
- redundancy
- checks
- software
- building plans
Let’s look at those in detail:
- redundancy
I expect portions of the junk DNA to be helpful in restoring broken segments elsewhere, either directly (by containing fragmentary copies of real genes), indirectly (by containing mechanisms that can ‘fix’ broken strands)
- checks
Checksum data for very important portions of our genome, without which failure rates might be higher than they are, think of this as ‘meta data’ that describes other parts of the genome.
- software
This is the big one, I fully expect that a portion of the DNA is set aside for a BIOS for the body that it belongs to, and because the software is intimately entwined with the hardware it is right there when needed (for instance while developing the brain)
- building plans
Proteins don’t magically assemble into bodies, if they would then medicine would be a piece of cake (just inject the right proteins and you’ll be fine, no matter what ails you). Instead we need some soft of high level map that guides the proteins during development to the right spots and degree of activity. The genome would be an excellent place to store such information, since it is copied from cell to cell during development.
Note that junk DNA (I use the term, even if I don’t believe there is any ‘junk’ in there) is one of those things that can only get smaller, as we understand more and more of our genetic heritage we will find that there is less junk, until eventually there is none left.
I’m really curious how long it will take us to drop that percentage below 50% and how long it will take us to relabel junk DNA as ‘not yet understood DNA’, or for lack of a better word ‘unidentified DNA’.