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| Science & Technology |
| Human DNA much more complicated then expected. |
| 2007-06-16 |
| The ENCyclopedia Of DNA Elements (ENCODE), an international research consortium organised by the National Human Genome Research Institute (NHGRI), part of the National Institutes of Health (NIH), today published the results of its exhaustive, four-year effort to build a "parts list" of all biologically functional elements in 1 percent of the human genome in the journal Nature. The ENCODE consortium's major findings include the discovery that the majority of human DNA is transcribed into RNA and that these transcripts extensively overlap one another. This broad pattern of transcription challenges the long-standing view that the human genome consists of a small set of discrete genes, along with a vast amount of "junk" DNA that is not biologically active. The new data indicate that the genome contains very little unused sequences; genes are just one of many types of DNA sequences that have a functional impact. The consortium identified many previously unrecognized start sites for transcription and new regulatory sequences that contrary to traditional views are located not only upstream but also downstream of transcription start sites. Other surprises in the ENCODE data have major implications for our understanding of the evolution of genomes. Until recently, researchers had thought that most DNA sequences with important biological function would be constrained by evolution making them likely to be conserved as species evolve. But about half of the functional elements in the human genome do not appear to have been constrained during evolution, suggesting that many species' genomes contain a pool of functional elements that provide no specific benefits in terms of survival or reproduction. Over the next couple of years the ENCODE project will be scaled up to the entire genome. The Ensembl project, a joint EMBL-EBI and Sanger Institute project, jointly headed by Ewan Birney, has already generated some initial genome wide datasets with early full scale datasets. This integration has lead to the identification of just over 110,000 regulatory elements across the human genome. "The goal for the next five years is delivering a more complete understanding across our genome" said Birney, "the ENCODE pilot project is the first step towards this goal." |
| Posted by:3dc |
| #6 nature usually doesn't lavish a lot of effort for no reason at all Zen, are you going metaphysical on us? I don't have any religion, as opposed to you, I just observe. ;-) |
| Posted by: twobyfour 2007-06-16 16:58 |
| #5 Without wishing to sound unimpressed (which I'm not), what else should we expect from several million years of evolution? I'm especially interested by their reassessment of "junk" DNA. While long intervals between vital coding sequences confers a degree of protection from ionizing radiation, nature usually doesn't lavish a lot of effort for no reason at all. This is especially so in light of how DNA remains a pinnacle of compact and concise information storage. The consortium identified many previously unrecognized start sites for transcription and new regulatory sequences that contrary to traditional views are located not only upstream but also downstream of transcription start sites. This isn't the huge surprise that it might seem to be. I would regard the downstream transcription start sites as "backup files" of these vital macros. But about half of the functional elements in the human genome do not appear to have been constrained during evolution, suggesting that many species' genomes contain a pool of functional elements that provide no specific benefits in terms of survival or reproduction. Again, not such a big shocker and they may well be wrong about how these functional elements "provide no specific benefits". A large library always provides more value even if a given individual does not read all of the books contained therein. Similarly, a large DNA catalogue of functional elements makes available many more viable mutations (read: adaptations) which can prove quite valuable if environmental conditions change downstream. All together, much as I would expect but still extremely cool. |
| Posted by: Zenster 2007-06-16 16:30 |
| #4 I second what 2x4 said. |
| Posted by: HalfEmpty 2007-06-16 09:08 |
| #3 God and the Scientist God is sitting in Heaven when a scientist says to Him, "Lord, we don't need you anymore. Science has finally figured out a way to create life out of nothing. In other words, we can now do what you did in the 'beginning' "Oh, is that so? Tell me..." replies God. "Well",says the scientist, "we can take dirt and form it into the likeness of you and breathe life into it, thus creating man." "Well, that's interesting. Show Me." So the scientist bends down to the earth and starts to mold the soil. "Oh no, no, no ..." interrupts God, I love this part) "Get your own dirt." |
| Posted by: BrerRabbit 2007-06-16 07:38 |
| #2 Wow. What's next? |
| Posted by: gorb 2007-06-16 06:21 |
| #1 Translation: The overlap during the transcription process indicates that there are several levels of encoding. The long repeating sequences (formerly deemed junk) may serve as a key (or keys) to decode other layers. Thus what may seem a simple sequence may be decoded in numerous ways, depending what is the actual position on the overlap that reading starts from. Lt's look a little closer. Imagine the DNA as a rope that is twisted from many strands (or rather loops which are then separated wrapped into chromosomes). This rope is again tightly packed, and held together with short strands of RNA that tie up several 'ropes' together. The tRNA that is usually specific to a certain code sequence approaches the packed DNA and unwraps a loop that is supposed to read, a little bit more of it as we learned above. It then acquires single amino acids from the cellular fluid and chains them according to the code (a mirror image). Somehow, it knows (I don't have a better word to describe it) where to look and how to call the singletons up. This is going at speed that if you could scale the nucleus up so you could see the process clearly, you would be enveloped in a 1000 mph whirlwind. Amazing, innit? |
| Posted by: twobyfour 2007-06-16 04:51 |