ONCE, it all seemed so beautifully simple. Our DNA, we thought, consisted of a set of recipes, or genes, for making proteins, and once we had identified them all and worked out what they do, we would be a long way towards understanding what makes us what we are.
If only. One of the big shocks that emerged from the human genome project was that we have only around 23,500 genes - barely more than a nematode worm. But in many other ways our genome is turning out to be dizzyingly complex (see diagram) .
"It is very difficult to wrap your head around how big the genome is and how complicated," says Ewan Birney of the European Bioinformatics Institute near Cambridge, UK, who is part of a major project to uncover the workings of the genome. "It's very confusing and intimidating."
For starters, rather than each gene coding for one protein, they often code for many. The coding parts of genes come in pieces, like beads on a string, and by splicing out different beads, or exons, after RNA copies are made, a single gene can potentially code for tens of thousands of different proteins, although the average is about five. Recent studies suggest up to 95 per cent of our genes may be alternatively spliced in this way. Even more astonishingly, in at least one case in humans, RNA copies of different genes are spliced together. If this is commonplace, it would vastly multiply the potential number of different proteins.
Another recent discovery is that instead of having two copies of every gene - one from each parent - we often have just one or three or more. This "copy number variation" is a result of big chunks of DNA being lost or duplicated, and could help to explain much of the normal variation between individuals, as well as diseases such as schizophrenia.
It's the way in which genes are switched on and off, though, that has turned out to be really mind-boggling, with layer after layer of complexity emerging. [NOTA DO BLOGGER: Uma predição feita pelos teóricos do Design Inteligente: mais e mais complexidade seria descoberta] Early studies suggested that gene activity was regulated mainly by transcription factors - proteins that bind to DNA, blocking or boosting the production of RNA copies of a gene and thus the amount of protein that gene produces.
While transcription factors do play a big role, cells also produce a wide variety of RNAs that, rather than coding for a protein, control gene activity. Some, dubbed small interfering RNAs (siRNAs), form complexes that seek out and destroy RNA copies of genes with a complementary sequence, preventing protein production. MicroRNAs work in a similar way but are not as specific, controlling the activity of many genes simultaneously. Piwi-acting RNAs, meanwhile, shut down the parasitic genes that litter our genome to stop them wreaking havoc, though it's not clear how.
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Read more here/Leia mais aqui: New Scientist
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NOTA CAUSTICANTE DESTE BLOGGER:
Notem a linguagem teleológica sobre o genoma: ações que descrevem sinais de inteligência. Notem a tentativa ilógica do autor em querer explicar a inteligência como sendo decorrente de não-inteligência. Onde foi que este moço estudou Lógica 101? Não sejamos tão crueis com ele, pois a Nomenklatura científica explica esses sinais de inteligência como derivados de não-inteligência, mero acaso e fortuita necessidade.
Isso é ciência? Não, não é. É a obstinada obtusidade para a manutenção do materialismo filosófico que posa como se fosse ciência.
Fui, não sei por que, cada vez mais convencido de que há muito mais podridão no reino da Nomenklatura científica para a manutenção de uma agenda ideológica. Por que os agentes da KGB (os revisores paritários em Portugal) ficam com raiva deste blogger quando menciono isso? É porque toco em um ponto nevrálgico deles: o câncer epistêmico que se alastrou e impede a prática de uma ciência saudável que se rende às evidências aonde elas forem dar.
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