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Jouw genen: meer virus dan mens

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What's really amazing is that there are a lot of these viruses in your genome. Scientists have identified about a 100.000 elements in your genome that came from viruses. Now, to put that in perspective we have 20.000 protein coding genes. That takes up about 1.2 % of our genome. Viruses, these things, take up 8 or 9 % So, you could say you're about 6 times more virus than human. If you're so inclined. So we are dealing with a time-scale that we carry in our own bodies. You start to get an unimaginably old period of time. I mean, I just marked with an arrow when the Grand Canyon formed. And you have viruses that are older than that in your own genome. This is a deeply weird concept. I mean, to think of our human genome having been gradually eroded as the Grand Canyon for millions of years by viruses. Now, our genomes didn't go willingly. We actually have lots of genes that seem to be specifically adapted for fighting off these viruses as they try to enter the genome and as they try to replicate. We try to put a stop to this. Because it can be very disruptive, I mean if a virus plops in and happens to plug itself where there is a really essential gene there can be trouble. A lot of retroviruses are causing cancer. So evolution has favoured defences against these things. But that's not to say that these viruses haven't ended up being useful. Actually mutations can essentially borrow some of the genes from viruses and use them to benefit us. My favoured example and the most startling one is is one that involves pregnancy. So, in order for an embryo a mammal embryo to develop - I should say a placental mammal embryo. It has to form a placenta which is attached to the uterus and in many groups of mammals what happens then is that there is a layer that forms here this sort of purplish cells here. That's a layer that allows the embryo to draw in nutrients from the mother and to attach to the uterine wall. And it is very distinctive because it formed by cells, but then the wall between the cells breaks down. So it's just a big open kind of layer of cytoplasm. Cell juice basically. There is a protein that makes that happen. If you knock the gene out from mice they cannot reproduce. It is fatal to an embryo not to be able to form that layer with that protein. That protein comes from a virus. Actually this is happened repeatedly in evolution. Different mammalian lineages have actually borrowed similar viral genes to make that layer. So, if it wasn't for viruses none of us would have even been born. -----

Video Details

Duration: 4 minutes and 9 seconds
Country: United States
Language: English
Views: 266
Posted by: ridelo on Jun 21, 2011

Wetenschapsjournalist Carl Zimmer legt uit hoe virale infecties door de geschiedenis heen het menselijk genoom hebben aangetast. Virussen vormen ongeveer 8 of 9 procent van ons genoom, zegt Zimmer. Verrassend genoeg zou de menselijke bevalling niet mogelijk zijn zonder een virale mutatie.

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