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Feb. 5th, 2005 06:10 pmThere's something happening in biology right now which I find incredibly exciting. There's an explanation for the junk DNA, and if it's right, it also explains all sorts of things - including the Cambrian explosion, when complex, multicellular life suddenly blossomed on Earth.
The idea is this. Most of our DNA isn't made of genes - the miniature programs which code for the proteins which build and run our cells. The coding parts are transcribed into RNA; that is, RNA copies of the program are made, which are used as blueprints for the cell to make those proteins. But the junk DNA is transcribed as well. If you assume it is just junk, this is incredibly wasteful. But it isn't junk at all. Those extra bits of RNA are a control system. A body as complex as a human being's needs an enormously long and complicated "program" to build it, and that extra RNA could be it. There's some evidence already - we already know about some RNAs which regulate cell development or are involved with disorders, meaning they have some function, they're not just garbage to be recycled.
The most exciting bit of this is the possibility that it explains the Cambrian explosion. For hundreds of millions of years, bacteria rule the Earth. Then suddenly, the multicellular organisms arrive, in a huge diversity of forms. The extra bits of RNA have to be edited to work properly, and bacteria can't do that, because they lack nuclei - there's no time to do the editing, the program is run immediately. Organisms with nuclei - plants, animals, fungi - can edit the RNA, and what's more, they have a specialised organelle to do it. The arrival of this "spliceosome" might have caused evolution to go into overdrive - for the first time, the control system itself could evolve, leading to complex bodies which had never been seen before on Earth.
Well, I'm excited. I was introduced to the riddle of junk DNA in my early teens - it's been a famous mystery for most of my life. Leader tape? Swap space? Advertising? Spam? (Is my explanation comprehensible, or is it gibberish?)
The idea is this. Most of our DNA isn't made of genes - the miniature programs which code for the proteins which build and run our cells. The coding parts are transcribed into RNA; that is, RNA copies of the program are made, which are used as blueprints for the cell to make those proteins. But the junk DNA is transcribed as well. If you assume it is just junk, this is incredibly wasteful. But it isn't junk at all. Those extra bits of RNA are a control system. A body as complex as a human being's needs an enormously long and complicated "program" to build it, and that extra RNA could be it. There's some evidence already - we already know about some RNAs which regulate cell development or are involved with disorders, meaning they have some function, they're not just garbage to be recycled.
The most exciting bit of this is the possibility that it explains the Cambrian explosion. For hundreds of millions of years, bacteria rule the Earth. Then suddenly, the multicellular organisms arrive, in a huge diversity of forms. The extra bits of RNA have to be edited to work properly, and bacteria can't do that, because they lack nuclei - there's no time to do the editing, the program is run immediately. Organisms with nuclei - plants, animals, fungi - can edit the RNA, and what's more, they have a specialised organelle to do it. The arrival of this "spliceosome" might have caused evolution to go into overdrive - for the first time, the control system itself could evolve, leading to complex bodies which had never been seen before on Earth.
Well, I'm excited. I was introduced to the riddle of junk DNA in my early teens - it's been a famous mystery for most of my life. Leader tape? Swap space? Advertising? Spam? (Is my explanation comprehensible, or is it gibberish?)
