So, for the novel, I’ve been doing lots of research on the history of genetics and I’ve come up with an odd problem about evolution. Most of our DNA is junk. It does nothing, codes for no proteins, just sits there like a big lazy telephone cord in every cell carried by every living thing on Earth. This is not news (I’m not the first one to discover this or anything) but my question is this: Why is it like that?
All that extra work every time a cell divides into two must be very time consuming and inefficient in terms of available primordial goop out of which these things are made, not to mention the energy overhead of carrying all that useless stuff around. It’s like carrying round armfuls of telephone directories when the only number you needed to remember could be written on a scrap of paper.
Why hasn’t the natural course of evolution cut the wasteful, unwanted bits out of DNA? That’s what the evolutionary process is supposed to do, right? Make the design efficient?
It seems to me there are two possible answers:
A) the ‘intelligent creator’ answer, which says the creator plans to use the spare bits of DNA to code for something really important in the future. He, or she, just hasn’t got around to it yet. After all, people might be willing to carry around a big notebook if they thought God was going to come along and add something interesting to it soon.
B) the ‘random chance’ answer, which says that if evolutionary change happens by chance mutation, you’ll get more mutations on a long DNA string than a short string, so maybe carrying around junk DNA is just a way of inviting serendipity to strike.
Can anyone think of a third possibility?
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It stores further information about us, the nature of which we are ignorant.
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Hi tottnm, certainly that’s a possibility, and I simplified my post by not mentioning that there are parts of the DNA strands that clearly have functions even though they have no genes, for example the repeating telomeres at the ends of strands that protect them from reproduction defects. There are however, long bits of each strand that seem to repeat the same apparently random sequence. Even if the sequence itself were saying something we don’t understand, I can’t see what useful information could be conveyed by repeating it thousands of times.
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This is not an original thought, but I read somewhere, and I thought it was one of your blogs but it obviously wasn’t, that perhaps the junk DNA was the important part for the gene and the part we consider essential is what the gene creates for us so we can carry it around
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Hi Margaret, I’ve certainly commented on junk in DNA before, but not quite in this context, I think. Remember, the cell doesn’t really need the genes in order to reproduce itself. The cell will keep on churning out copies of itself even if there were no useful genes coded within its DNA. The genes allow the cell to churn out proteins that build muscle, bone and other bodily structures, but put it in a nice test tube of nutrients and the cell will reproduce whatever genes it does or doesn’t have along its DNA strands. So, I guess the question is, are the genes just a sideshow that seeks to keep the cell in a nice warm environment in which to reproduce, or is the cell’s main purpose to be a reproducible library of genes for the living container?
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Hi David. I really appreciated your post. Something that I always try and remember, because I think it is such a beautiful thing, is that evolution is not an efficient machine. Because it is random and spontaneous, “junk” DNA can build up rapidly and remain for very long periods of time. Unfortunately, I can’t provide you with a source for this. Sorry!
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Could the excess be treasures in the attic? Half-baked snippets once intended to become full-fledged stories. Answers to questions never asked.
A little more practically, Microsoft’s products are rife with excess code, written over time by anonymous developers who each added functionality without first cleaning the slate. Perhaps DNA accumulated over time? Or perhaps it was designed by committee?
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Richard Dawkins discusses this at length in the Selfish Gene. Fascinating discussion.
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Kim, I keep meaning to read the Selfish Gene, but then – just as I work up to it – Dawkins comes out with one of those self-publicising statements that are clearly put out there because he believes controversy sells and then I slip back into believing he isn’t really a serious scientist. I must overcome this prejudice and give him a chance. (P.S. I’d like to believe the excess DNA are treasures in the attic, but a lot of it seems to be the same random short sequence repeated over and over again. I imagine these more like the blank pages of a notebook that haven’t been written in yet, which leads me back to the question ‘Why are we carrying a notebook that’s much bigger – and heavier- than the story we’re carrying around?’)
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Perhaps DNA is like a certain author I know , and these are all the discarded first chapters.
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LOL – full disclosure – I loved the first 3/4 of the book and was never able to make it to the end. But those first chapters introduced concepts that blew my 16 year old mind 🙂
Sometimes an SOS is sent repeatedly. Although these sequences appear to be “garbage,” I suspend my disbelief – wonder if there are variations we haven’t detected.
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