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I've been thinking about it, and I think that we can actually pretty much guarantee epigenetics played a truly massive part in creating the diversity of life we see. My basis for saying that is this:First let's look at what we know:1. Epigenetic mutations are not permanent changes to the genome.2. Epigenetic mutations can happen very quickly.3. Epigenetic mutations will continue as long as the element which stimulated it persists(plus a few generations for good measure)So based on this, we can expect that many life forms have been exposed to stressors which evoked an epigenetic response in the past. As soon as any epigenetic trait begins to be expressed it is subject to natural selection.Hypothetical: Mutation A(epigenetic) deals with Stressor B. Stressor C is only slightly dealt with by Mutation A. Mutation A + Mutation D(genetic) can deal with Stressor C. At this point, Stressor B can disappear and Mutation A will still remain because it has become something more through natural selection.Since epigenetic mutations are both specific responses to environmental conditions and much faster than genetic mutations, and subject to natural selection as anything else it is clear they probably play a huge part in the diversity of life.I know this doesn't prove that epigenetics could "choose" mutation, but since the epigenome is subject to natural selection; then simply by mutating, life is providing or choosing a route for natural selection to work on.
I know this doesn't prove that epigenetics could "choose" mutation, but since the epigenome is subject to natural selection; then simply by mutating, life is providing or choosing a route for natural selection to work on.
Quote from: norcalclimber on 18/04/2010 02:46:56I know this doesn't prove that epigenetics could "choose" mutation, but since the epigenome is subject to natural selection; then simply by mutating, life is providing or choosing a route for natural selection to work on.This all sounds very logical and sensible - but things that are subject to natural selection appear to make "choices" only after the fact - they're not choices, they're reactions, so we're back to the status quo, only with some epigenetic factors also being selected for/against.
If you look at the situation where genetic changes have been enforced, e.g. dogs, you have an artificial species, though with a wolf genome. If people disappeared tomorrow, dogs would be wolf food 'on the hoof' and would likely disappear in a few generations. The alternative would be for the environment to alter itself to accommodate them, unlikely unless we hunted the wolves to extinction first. Even then, the dogs would evolve back into wolves, indistinguishable, as the environment is still king. The rules of evolution were set billions of years ago, and no amount of wish fulfillment will change them.
What is the epigenetic transmission method from parents to children? I got the impression that it might only be possible for the male to pass on epigenetic information that was the result of some external influence. The female (mammal at least) cannot, because the female does not produce eggs after birth, so, in a sense, the epigenetic information from the mother is "locked in" from a very early stage.Or did I get that wrong?There are interesting analogies betwen these mechanisms and control systems (systems with feedback). Natural selection is a very heavily damped control mechanism (it has a lot of negative feedback.) Epegenetic modification has a very fast response with a slow decay (it's like a sawtooth). Together, they would seem to steer evolution through interaction, but understanding what the overall response actually is probably going to take an awful lot of work 
The rules of evolution probably themselves evolved. There would have been competing systems such as immortal lifeforms (until something fell on their head) but evolution obviously won out, probably fine-tuning itself in the process to the perfect system it is today. Wolves did not evolve forward to become dogs. When mankind's experiments in epigenetics end nature will regain her normal course, and it won't include dogs. If dachshunds could exist outside of their artificial environment, the woods would be full of them.
The genes for that are still in their genome and can be expressed by careful breeding
None of their ancestors could fly, so you can't breed a flying dog
If epigenetics worked, you should be able to do that by throwing dogs out of airplanes until they got the picture. Sorry, that would be a cruel thing to do, lawyers maybe, but not dogs.
It's just that there are so many unexpressed genes from countless generations previous that any new trait is almost certainly a re-expression of an old gene rather than the creation of a new one. Most species have different lineages so any genetic damage would be canceled out as they interbreed. It's just the law of averages. If they become too inbred they are usually headed for extinction. Epigenetics won't save them.
I think this is contrary to what is at this point in time happening to the Tassie Devil.prior to the devil's facial tumors their genetic pool was limited. Scientists say within 10 years the entire species could have been wiped out due to their limited gene pool, stating that they were almost clones of each other.After the cancer they adapted and breed at a younger age, (I find that amazing) able to pass on some of the immunity to their offspring before they die. Now there is a breeding program in place that takes the non infected devils from captivity to breed with the more diverse genetic pool (since the cancer) in the wild. I beleive this is an example of epigentics and evolution
That would seem unlikely. I have not calculated what the number would be, but the possible number of permutations of a genome that's as long as the human genome must be an incredibly large number. I'm sure there are lots of opportunities for the creation of new genes.
Quote from: Geezer on 21/04/2010 03:28:28That would seem unlikely. I have not calculated what the number would be, but the possible number of permutations of a genome that's as long as the human genome must be an incredibly large number. I'm sure there are lots of opportunities for the creation of new genes.There are lots of ways to arrange the cards in a deck, but most arrangements are losers. I think evolution has found all the winning arrangements for the game we play (our environment). If the environment changes, new arrangements can become valuable, but most changes would be covered by genes from the past. Don't throw out your old steam engine!
I agree, but the existing species are in tune with the existing environment which flows from the laws of nature. New adaptations cannot shoulder their way in just because they are, say, more politically correct. The environment must have a place for them to fit in without changing the laws of nature to accept them.
Due to the changing laws of nature whether human influenced or not, including the time factor, the ever adapting multitude of species struggle to survive and appears to always have.
Quote from: echochartruse on 21/04/2010 23:57:41Due to the changing laws of nature whether human influenced or not, including the time factor, the ever adapting multitude of species struggle to survive and appears to always have.I was hoping I could change 2+2 to equal 17 for a second so I could make a quick killing on the stock market but I realized that by the end of the second the universe would have exploded.
Maybe not the changing laws of nature, but the environment is always changing ever adapting.
If the epigenome tells a cell what type of cell to be, isn't it plausible that cancer may actually be epigenetic?
Cancer is an epigenetic disease at the same level that it can be considered a genetic disease. In fact, epigenetic changes, particularly DNA methylation, are susceptible to change and are excellent candidates to explain how certain environmental factors may increase the risk of cancer. The delicate organization of methylation and chromatin states that regulates the normal cellular homeostasis of gene expression patterns becomes unrecognizable in the cancer cell. The genome of the transformed cell undergoes simultaneously a global genomic hypomethylation and a dense hypermethylation of the CpG islands associated with gene regulatory regions. These dramatic changes may lead to chromosomal instability, activation of endogenous parasitic sequences, loss of imprinting, illegitimate expression, aneuploidy, and mutations, and may contribute to the transcriptional silencing of tumour suppressor genes.
DR MARCUS SCAMMELL, MARINE ECOLOGIST: The Tasmanian Government’s conclusion was that it was naturally occurring toxins and therefore it’s okay....DR MARCUS SCAMMELL, MARINE ECOLOGIST: Everything that we knew could cause toxicity we had eliminated.....DR CHRIS HICKEY, ECO-TOXICOLOGIST, NATIONAL INSTITUTE OF WATER AND ATMOSPHERIC RESEARCH, NZ: It told us we were looking for something different, something unusual. I think they really may have stumbled on something quite new.
Because what disease in wildlife populations tends to be is a harbinger of instability, of a breakdown in normal cycles of a population reaching a stable balance with other animals interacting with their ecology. And perturbations, whether they are human induced, or the fact that we’ve actually through our agency allowed for the introduction of new pathogens. This is the brave new world that we face in the 21st century.
In order to identify the tissue of origin of the tumors, the team used the Genome Sequencer FLX System to sequence both diseased and healthy transcriptomes-- the complete set of genes that are “turned on” in a specific cell. The researchers then compared gene expression results between the two tissues and found that the tumors’ genetic signature best matched that of Schwann cells found in the peripheral nerve. The underlying mechanism for how these nervous system cells spawned cancer cells is still unknown.....Murchison et al. The Tasmanian devil transcriptome reveals Schwann cell origins of a clonally transmissible cancer. (2009).
DR MARCUS SCAMMELL, MARINE ECOLOGIS............St Marys is surrounded by natural forest. And we’ve found no evidence of toxicity in the St Marys catchment. However in the St Helens catchment directly below this monoculture of plantation trees, we had permanently present toxin.DR ALISON BLEANEY, GP & LOCAL COUNCILLOR (at South Georges River): This is the head waters of the South George which feeds into the George River, and here we are surrounded by plantations. This used to be natural bush and farming land and now we are completely surrounded by plantations here - the Eucalyptus Niters. This is the source of our drinking water for St Helens, let alone all the animals that drink from it, and this is one of the areas where we’ve discovered that the water in fact is toxic. This should be the most pristine water. This is the very head waters of the South George. Where is this toxin coming from?(Excerpt of Dr Alison driving to visit patient)DR ALISON BLEANEY, GP & LOCAL COUNCILLOR: I’m off to go and see a patient who’s got a very... a very rare cancer - Waldenstrom’s Anaemia. She’s one of only approximately 18 in Australia, and we just happen to have two in St Helens. And in the last perhaps six years or so we’ve actually seen quite few people with really quite rare autoimmune diseases of their brain for instance. We’ve had a case of Wegener’s Granulomatosis; it’s actually quite a rare disease.So now looking back on this over the last ten years, I realize that I see many things now that as a GP... that many GPs would never see one of these cases in their working lifetime. Clearly in a population of less than 3,000 to have these rare diseases - to have this chronic ill health - there must be something on the go to explain this.
Possibly the trees have introduced a new toxin into the environment which is causing cancer in the human population and wildlife. The lineages of the populations that are susceptible to this will die off and those lineages whose genetic structure can cope will survive. The Tasmanian Devils have no immunity because some event in the past reduced their numbers to a few mating pair and all devils extant are descended from them. This lineage lacks the genetic protection or it has been damaged.
One aspect of the epigenome which I find extremely interesting is that both advantageous and deleterious traits seem to be passed on by the actions or experiences of an organism; i.e. In the Time article I cited a bit back, the descendants of those who had experienced times of extreme abundance in food were actually less fit than descendants of those who had to struggle.I guess what I am curious about with this is: In the past(and present) an omnipotent creator watching over us constantly has been used to encourage morality and balance in life; I personally do not believe in said creator, but could the epigenome replace that? If all our actions and choices will be passed on to future generations, am I potentially dooming my children and grandchildren by my actions?
http://www.sciencedaily.com/releases/2009/10/091009104646.htmhttp://www.sciencedaily.com/releases/2007/12/071214094106.htmDefinitely intelligent process.
The amazing thing about our genome influenced by our actions today which influence following generations is that there is 'choice' definitely not 'random'. The fight for survival is calculated.
It doesn't entirely depend on you passing on the diseased gene but also what the next generation does with it. As someone said earlier here, just because a family has long generation of say breast cancer/ alcoholism, diabetes, whatever doesn't mean every person there after gets the genetic diseaseThere is choice which some see as Random.
Maybe the 'creator' is not a man but a protein or something entirely new/undiscovered within the proteins that control and process changes in our genome.
Tibetan highlanders began to genetically adapt to prevent polycythemia, should their children live at lower altitude then their genetic adaptations would alter to suit the conditions over just a few generations.Whatever the source is for the process's initiation for our genome to cope, it is not random but logical and calculative.
It will be very exciting when we find what actually determines which genes are expressed.http://www.sciencedaily.com/releases/2009/10/091009104646.htmhttp://www.sciencedaily.com/releases/2007/12/071214094106.htmDefinitely intelligent process.