<p>Epigenetics is freaking magic.</p>
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<p>Epigenetics refers to changing heritable traits and passing them to offspring without changing the DNA sequence. In terms of etymology, “epi” means “on top of” or “in addition to”. Normally, to change heritable traits you have to have a mutation in the DNA sequence. </p>
<p>Stepping out of the world of epigenetics for a moment to illustrate a relevant principle, DNA is transcribed into mRNA by having a protein bind to a promoter sequence upstream of the relevant gene. Other proteins called transcription factors may bind to the DNA sequence near the promoter element to either (1) stimulate transcription by making this binding more energetically favorable or (2) to repress transcription by blocking this binding. Epigenetics works by a similar principle–a chemical modification either activates an existing gene in the sequence or represses it. There is no creation of genes in epigenetics.</p>
<p>There are two main mechanisms by which epigenetics work. First is chemical addition of a methyl group to a part of the DNA sequence (there is one specific sequence on which this may occur – cysteine nucleotide separated from a guanine by a single phosphate group.) The methyl group works as a transcription repressor to silence a nearby gene. </p>
<p>The other mechanism is modification of histones, the proteins which DNA is wrapped around in the cell. Methylation of strands that hang off the histone protein (aka histone tags) make packing of several histones (with their DNA wrapped around them) more difficult. If histones are tightly packed, the DNA that is buried in a bundle of histones cannot be transcribed. Since the histones aren’t as tightly packed, more of the DNA is exposed and can be transcribed. So the histone methylation activates gene transcription.</p>
<p>Methylation of DNA or histones can be triggered by outside signaling, which may originate from some outside stress the organism is experiencing. It means that changes to the genetic code to respond to the environment can be achieved a lot faster compared to natural selection after random mutation. From the Lamarckian perspective, a hypothetical scenario would be the stretching of a giraffe’s neck to reach a high-hanging fruit. There aren’t a lot of studies actually linking an outside stress of a population to epigenetic changes. The one study I’ve seen is where an outside stress causes epigenetic changes is one in which a famine in a particular town about 80 years ago triggered bad health outcomes in their children.</p>
<p>Radical. So epigenetics changes the expression of the existing DNA rather than mutating the sequence? Like certain lightswitches are turned on and off as opposed to installing or rewiring them? </p>
<p>Apologies for elementary questions - the last bio class I took was in 10th grade! (this is a safe space. this is a safe space. this is a safe space).</p>
<p>Excellent summary by collegealum314. The wikipedia article on epigenetics is pretty good, too, in my opinion. You have the essence of it MITChris–the only thing I would add to your one-sentence summary is that the changes in gene expression are heritable, which is really pretty wild.</p>
<p>I think that the next 25 years or so will see a great change in our understanding of gene expression.</p>
<p>Btw, Roman or Holocaust history is different because we have first-hand accounts. Not comparable.</p>
<p>All this may just show that when you put together a group of highly intelligent individuals, they may tear apart the questions in unpredictable ways.</p>
<p>Thanks QM and collegealum314. I learned of epigenetics by trawling through some blog posts but the fundamentals escaped me.</p>
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Ditto.</p>
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This is true, but the point is that current scientific knowledge isn’t the be all, end all of how the world around us truly functions. The fact is that it’s constantly changing.</p>
<p>“Picture a scientist as working on part of an enormous crossword puzzle: making an informed guess about some entry, checking and doublechecking its fit with the clue and already-completed intersecting entries… Rival teams squabble over some entries, pencilled or even inked in and then rubbed out, perhaps in a dozen languages and a score of times. Other teams… call to teams working on other parts of the puzzle to see if they already have something that could be adapted, or to ask how sure they are that it really must be an S here… Now and then a long entry, intersecting with numerous others which intersect with numerous others, gets erased by a gang of young turks insisting that the whole of this area of the puzzle must be re-worked, this time, naturally, in Turkish-while others try, letter by letter, to see if most of the original Welsh couldn’t be kept …. I don’t mean to fob you off with a metaphor instead of an argument. But I do mean my word-picture to suggest… that scientific inquiry is far messier, far less tidy, than the Old Deferentialists imagined; and yet far more constrained by the demands of evidence than the New Cynics dream."
The entire explanation can be found here: [Scientific</a> knowledge ? reliable but not certain | Open Parachute](<a href=“http://openparachute.■■■■■■■■■■■■■/2012/05/31/scientific-knowledge-realiable-but-not-certain/]Scientific”>Scientific knowledge – reliable but not certain | Open Parachute)
I’ld really recommend it. It’s wonderful.</p>
<p>Looking Forward,</p>
<p>We may not have a first hand written account of evolution, the evidence from geology, Biology and other sciences, is much more definitive and definitive than first hand accounts.</p>
<p>In reality, the only people that disagree that the macro story of evolution have either not considered the evidence, choose not to accept the evidence because they think it conflicts with their faith, or are misinformed.</p>
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Of course not, but in the case of evolution, we as a profession are so far beyond debate about whether evolution exists. This feels to me like a chemist having to argue that molecules exist, or a physicist having to argue that gravity exists. The interesting debates in the field are not about whether evolution exists. They are about the ins and outs of the thing – the mechanisms, the history, the ways the process can be co-opted for our own purposes.</p>
<p>There’s very little that makes sense in modern biology without evolution by common descent being true.</p>
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Well, there’s actually nothing in the theory of evolution by common descent that strictly stipulates that humans must have evolved by purely naturalistic processes – just that it appears, by every way we can look at it, that humans evolved by purely naturalistic processes.</p>
<p>You can take several tacks here: that humans evolved from earlier great apes by purely naturalistic processes, but that at some point God provided the Secret Sauce of Ensoulment; that God provided the holy genetic poke that caused a small band of apes to break off from the larger breeding pool of their compatriots and acquire certain important mutations in Foxp2 or Aspm or what have you. There are plenty of positions that are consistent with the available evidence.</p>
<p>Chris, just to add to your trove of knowledge, there are also proteins called transcription factors that participate in controlling the on-ness or off-ness of other genes. The transcription factor can bind to the region ahead of a certain gene and cause it to be transcribed, or cause it to be repressed, or recruit the proteins that modify chromatin, as collegealum described above. So in addition to the chromatin marks themselves, the levels of transcription factor expression are important. </p>
<p>A gene I like (GIL) is expressed at high levels in a certain kind of neuron (1), and lower levels (about 0.5x) in a neighboring kind (2). In the absence of my most favoritest gene (MMFG), GIL expression in the two populations is equivalent, and the 2 neurons turn into 1 neurons.</p>
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<p>To expand on this, the epigenetic modifications to the DNA sequence are like “transcription factors” attached by a strong covalent chemical bond, whereas normal transcription factors bind through weak noncovalent bonds. These covalent bonds are strong enough to survive cell division and thus the passage of the gene modification from parent to progeny. Because they are bound by noncovalent bonds, the binding of normal transcription factors are weak and in constant equilibrium between bound and unbound state. Also, the methyl groups that entail the epigenetic “transcription factors” are much smaller than normal transcription factors, which are proteins.</p>
<p>Note that my usage of epigenetic “transcription factors” is nonstandard; it is just to illustrate a comparison.</p>
<p>man science owns</p>
<p><em>Cracks whip over MITChris’s head</em> </p>
<p>Stop learning and get back to your application reviews!</p>
<p><em>Cracks whip over heads of students who have read this thread and not yet applied</em></p>
<p>Don’t write any essays on epigenetics!</p>
<p>[Mice</a> Inherit Specific Memories, Because Epigenetics? ? Phenomena: Only Human](<a href=“http://phenomena.nationalgeographic.com/2013/12/01/mice-inherit-specific-memories-because-epigenetics/]Mice”>Mice Inherit Specific Memories, Because Epigenetics?)</p>
<p>Two weeks ago I wrote about some tantalizing research coming out of the Society for Neuroscience meeting in San Diego. Brian Dias, a postdoctoral fellow in Kerry Resslers lab at Emory University, had reported that mice inherit specific smell memories from their fathers even when the offspring have never experienced that smell before, and even when theyve never met their father. Whats more, their children are born with the same specific memory.</p>
<p>@Much2learn I think you meant to say micro-evolution.
@molliebatmit Exactly what I mean - there was some God power involved. However, the question that was given was the following:
89% of respondents believed that humans and other living things evolved due to natural processes or that a supreme being guided the evolution of living things.
Basically, if you say “Yes,” you mean that it happened with NO supreme being. Hence, the question isn’t really “Do you believe in evolution?,” and this is why people voted “No.”</p>
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<p>This wording from the Tech article actually doesn’t make any sense. </p>
<p>Let A = belief that humans and living things evolved because of natural processes
B = God guided the evolution of living things</p>
<p>B sounds like it is equivalent to intelligent design, but I’m not positive. It could just be God-aided evolution. </p>
<p>Anyway, using mathematical notation, if B is equivalent to intelligent design, then basically everyone should fall under the set {A or B}. The Tech article says that 89% of responses are members of the set {A or B}.</p>
<p>@collegealum314 - yes, that mice memory study is what introduced me to the concept of epigenetics!</p>
<p>@collegealum314 When referring to the original question, yes. It’s:
Choice A - evolution is real, but guided by nature.
Choice B - evolution is real, but guided by God.
Back to the original question, then - “Who believes in evolution?” => the answer is 100% of responders.</p>
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<p>What evidence? Are you referring to the fossil record? Have you ever considered what it takes to create a fossil?</p>
<p>Assume that 1" of sediment is equivalent to 1 million years. Assume that a fish is 1" thick, and happens to fossilize on its side (lowest profile). How is that fish suppose to survive intact for 1 million years? Scavengers and bacteria are very efficient and would not last a few days. Fossilization generally requires catastrophic events (rapid burial). That is inconsistent with the assumption of slow accumulation of sediment.</p>
<p>Regarding belief in “evolution”. There is Micro Evolution (variation within a species) and Macro Evolution (changing of one species into another). Evolutionists routinely make the logistical error of using proof of Micro Evolution as proof of Macro Evolution. Micro Evolution is a POTENTIAL method of Macro Evolution, but is not proof of Macro Evolution. If you ask the general question “do you believe in evolution”, then 100% of the people should answer “yes”. You would have to be a ■■■■■ to not believe in (Micro) Evolution. The more interesting question is the specific one of: Do you believe in Macro Evolution.</p>
<p>Note: In the USA, evolution has become politicized. In other countries, like China, there is not the same level of indoctrination. So, while they may “believe” in Macro Evolution, they are open minded about the science supporting it. I recall that a few years ago, there was a conference in China where they discussed that there is inadequate evidence in fossil record to support Macro Evolution. That is not to say that it may not eventually have enough evidence, just that the current evidence is insufficient.</p>
<p>Opera Dad,</p>
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<li><p>I am not sure that I understand your fossil argument, but it sounds like you are suggesting that all fossils must have been formed after say, a great flood. Is that correct? </p></li>
<li><p>I am not going to attempt to recapitulate the evidence for evolution here. There is a lot of it and it takes too long. However, in an earlier post on this string, I suggested several easy to read books on the subject. The fact that you ask “what evidence?”, suggests to me that you have not taken the time to educate yourself on the subject that you are arguing against. Why argue against it if you do not understand the facts and evidence? </p></li>
<li><p>You argue that scientists are not open minded, but that is another canard. It is the nature of every scientist that I have ever known to challenge everything, and not take things for granted. You must know that. There is a big disincentive for scientists to accept evolution because, if evolution were wrong, and they could provide evidence, they would get a nobel prize, become rich, and become famous. They accept the evidence because they have considered the evidence and it is clearly correct, not because they are closed minded.</p></li>
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<p>I would be happy to change my view if there were evidence. The facts are that it is the opponents of evolution who will not objectively consider the evidence. That is why, to my knowledge, there aren’t any educated opponents of evolution left who are not a member of a religion that has an issue with it. Are you aware of any?</p>
<p>Furthermore, it would be easy to disprove evolution if it did not happen. One fossilized T-Rex with a person (or a bunny rabbit, or a chicken, or a dog) in its stomach would do it. So why aren’t any of the highly opposed religious groups out in Utah trying to find one? Because, like me, the few of them that really examined the evidence know that it is a waste of time and money because the evidence is overwhelming.</p>