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Opposable Thumbs and Upright Walking Caused By "Junk DNA"
quinnlynn writes "A group of research scientists at Yale discovered that the evolution of opposable thumbs and upright walking in humans is due to changes in the genome in the areas still classified as "junk DNA." Quoting: 'Results from a comparative analysis of the human, chimpanzee, rhesus macaque and other genomes reported in the journal Science suggest our evolution may have been driven not only by sequence changes in genes, but by changes in areas of the genome once thought of as "junk DNA." ... Researchers have long suspected changes in gene expression contributed to human evolution, but this had been difficult to study until recently because most of the sequences that control genes had not been identified. In the last several years, scientists have discovered that non-coding regions of the genome, far from being junk, contain thousands of regulatory elements that act as genetic "switches" to turn genes on or off.'"
Yale has also recently completed sequencing the Trichoplax genome. Trichoplax has the simplest known animal genome, and it shares 80 percent of its genes (comprised of 98 million base pairs) with humanity. Professor Stephen Dellaporta was quoted saying, "We are [excited] to find that Trichoplax contains shared pathways and defined regulatory sequences that link these most primitive ancestors to higher animal species. The Trichoplax genome will serve as a type of 'Rosetta Stone' for understanding the origins of animal-specific pathways."
In defense of DNA fingerprinting it is often stated that the databases only store non-coding DNA, so there is no risk that someone might be able to centrally deduce possible health problems and other traits which could negatively affect the individual. How does that argument hold up now?
I have always found it irksome when biologists claim that a high percentage of our DNA is just junk (do-nothing) DNA. It's as though they were saying "we of course know what it does: It does not do anything". Why not say "we don't know what it does, if anything at all"?
Most of them do, "Junk DNA" is a handy phrase and one that's been picked up by the media, the majority of Biologists are quite open minded on the subject. The fact that a lot of it is translated in to RNA even lends wait to the argument that it is of functional value. Aside from that things like telomeres (the ends of DNA that get eaten away as the replicates) and centomeres would be labelled as "junk" even though they have obvious functional value. Most scientists just use "junk" as a synonym for "non-protein coding" as a kind of shorthand.
We'll eventually discover that DNA is just instruction tape for a type of turing machine which generates our entire body as its output. As we all know, Turing machines require lots of repetitive instructions to operate because they're so limited in their actions.
'I'd love to see the results of removing Junk DNA from a human's genome, and then pump it into an egg and grow it up all normal like and see what kind of walking cancer emerges.'
Well, Nature has (sort of) done this experiment already. The Fugu (pufferfish) genome has a highly 'compressed' genome, with about the same number of genes as mammals, but a much smaller complement of non-coding DNA:
http://genomebiology.com/2002/3/9/comment/1012
So it's certainly possible for an 'advanced' species to survive without the 'burden' of much of this material (obviously the regulatory elements are still required, but a lot of the highly repetitive stuff seems to be dispensable). Of course the 'junk DNA' may still confer evolutionary advantages (as the linked article put it: 'it may in fact be the clay from which evolution fashions morphogenetic changes'), and perhaps it says something that mammals have in general evolved in what most of us would regard as a much more interesting way than pufferfish...
This is hardly new. It has been recognised for some time that so-called "junk" DNA is nothing of the sort, but is almost certainly associated with gene expression to some degree.
The cool thing here (and what, I hope, will keep me in a job for a while) is trying to work out how.
(The fun aspect of molecular biology is that so much changes even over the course of a 4-year degree course... - and to think I nearly went into maths, where I wouldn't be doing anything remotely cutting-edge until PhD level...)
I'd love to see the results of removing Junk DNA from a human's genome, and then pump it into an egg and grow it up all normal like and see what kind of walking cancer emerges.
Unless you also modified the host's DNA as well it might well do nothing. Chickens have genes for growing teeth and long tails, which are simply switched off.
Junk DNA doesn't exist. It's just DNA we don't understand.
Some of it probably is actually junk. Where DNA performs no function at all there is no evolutionary effect to weed out harmful mutations. Though it's possible that many mutations of an "obsolete" gene may result in something useful.
If DNA is observed which dosn't vary much between individuals (or even species) then that tends to imply that it functional (possibly even very important). Even if we currently have no idea what that function actually is.