This topic contains 8 replies, has 1 voice, and was last updated by Profile photo of Beth_Ailis Beth_Ailis 4 years, 10 months ago.

Epigenetics — the programming for your DNA

  • Profile photo of Beth_Ailis

    I think I need to stay at th Nova level, not being all that science-minded. But I’m glad you posted. Very interesting reasearch going on.

    Profile photo of Dave Johnson

    I recently went back to college part time to study Biology and the part of the course we are studying at the moment is DNA and cell division and specification. My favourite part of the course so far and well fascinating. I have found though that at the level I study the course does not get too in depth and expression of genes to affect cell function seems to have been skipped over (hopefully we’ll come back to it later as the course seems to bounce back and forth between related subjects). In the mean time I’ll be happy to read anything you post regarding genetics and would be particularly interested in how genes “switch on” to determine what the daughter cell is to become. I understand the basics of chromosome compaction and the phases of mitosis and meiosis etc (being a 30 something year old returning to A-level Bio) so if you can pitch it at that kind of level (similar to above) if possible that would be awesome. But that said I’ll read anything about genetics even if it is pitched way above my intellectual punching weight.

    Ta very muchly

    Dave

    Profile photo of James Thorne

    Hi all,

    I thought i would write a little piece about Epigenetics. I am working in a lab in the UK and this is the sort of stuff i work on.

    Epigenetics is classically defined as inheretence without alteration to the DNA sequence. Essentially though it is inheretence at the cellular level, not organisms. So when a stem cell asymetrically divides, it will produce two daughter cells, another stem cell and a blood cell for example. Epigenetics determines how these two different cell trypes, with identical DNA, can be derived. The epigenetic processes at work switch of some developmentally required genes, and switch on others, thus transforming the fate, function and behaviour of the cell. For those of you out there with some biological degree, this is essentially what Lamark described in his view of evolution (the competing theory to Darwin in the late 1800’s). It appears he wasn’t so far off the mark after all. Now though the term has been broadened to include regulation of gene expression but does not neccessarily require the daughter cells to ‘remember’ these changes.

    There is a huge amount of DNA in each individual cell, about 2 meters if it were laid out in a line. However it is very thin so is able to be packaged into the nucleus of the cell, and is done so in a highly organised and efficient way through an interaction with Chromatin. Chromatin is essentially the name given to the protein case which wraps around DNA. DNA is wrapped around specific protein complexes called nucleosomes (146bp of DNA around 1 nucleosome and about 54bp of ‘linker DNA between nucleoomes). The nuceosome complexes (made of 8 histone proteins) have ‘loose and waving about’ tails. They determine how tightly the DNA is coiled up, whether other proteins can see the DNA and physically interact with it, they determine if a gene can be expressed (like the haemaglobin gene in a red blood cell) and turned into protein or if it will be permanently silenced (as in the case of a blood cell gene in a neuron) or transiently silened as in the case of most genes in stem cells.

    The histone tails confer these characteristics through what are called ‘post-translational modifications’ (PTMs), this is a term we give to changes (covalent) made to a protein after it has been translated from the RNA intermediary between DNA and protein. (DNA is traanscribed to RNA which is in turn translated to protein). The PTMs confer huge amounts of extra information to the protein, such as its activity level, its interaction partners and even the affinity it has for DNA. So when histone tails become methylated (a form of PTM) their affinity for DNA increases, thus winding up the DNA into tighter and tighter coils so it can not be accessed by the molecular machinery which allows genes to be expressed through the process of transcription (writing DNA into RNA, before the RNA is tranlasted to protein). On the flip side to this is acetylation (another form of PTM). Acetylation actually reduces the binding between DNA and the histones thus relaxing the DNA chromatin structure and exposing the DNA to the nuclear meliue where it can be access by the transcription machinery.

    The balance between methylation and acetylation are at the heart of modern Epigenetics, their levels are determined by many factors, but other genes, your food and exercise levels as well as disease play the leading roles.

    If any of you want to find out more then Wikipedia is a good place, you can search for terms like TriThorax and PolyComb, Histone and nucleosome, DNA compaction, enhancers, promoters and transcription start sites and transcription factors.

    Also, if you want any more from me then let me know an i can try to give a few specific examples. I will try to post some more on epigenetics and how it relates to some elements in Siglers novels, there is probably quite a bit.

    James

    altruism is a true rarity

    Profile photo of Insignificant Blood Splatter

    With such high reccomendations, how can I possibly stay away? If my dad restarts our membership to netflix (what the heck does that mean?), I’ll mention it to him. Not sure if my mom or sister would like it, but I don’t need them to watch the movie with me, anyway. :P And if I can’t catch it before i go back, I’m sure the geeks at my school have downloaded it. If not, they can easily be persuaded (probably even without violence…) ;)

    "Urban legends go well with parmesan and horror. In fact their name is conveniently one and the same: Stevie." {UNdead GirlCo Knight for Sigler}

    Profile photo of sadock

     It’s #8 on my all time best Science Fiction Top Ten List.

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    GirlCo: Quieter than ninja, faster than Sklorno, stronger than Ki, and more devious than the Quyth

    Profile photo of Insignificant Blood Splatter

    That’s exactly it. Thank you.

    Huh. This is like the 5th time I’ve heard ‘Gattaca’ mentioned within two or three days. I think I must find and see this movie.

    "Urban legends go well with parmesan and horror. In fact their name is conveniently one and the same: Stevie." {UNdead GirlCo Knight for Sigler}

    Profile photo of sadock

     You’re talking about making designer babies, right?

    Essentially the parents could choose what color eyes, hair, how tall, etc. Of course, all of that would be limited by the raw materials the genetic engineer began with. So if you had parents with poor genes, your options wouldn’t be all that good regardless of how much you tweaked things. 

    I loved the movie Gattaca because it dealt with this subject in a fairly entertaining way. Not exactly a realistic way, but it was still a fun ride.

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    GirlCo: Quieter than ninja, faster than Sklorno, stronger than Ki, and more devious than the Quyth

    Profile photo of Insignificant Blood Splatter

    This reminded me of – what’s it called – genetic… Genetic something. Like choosing what your child will look like, their gender, and pre-testing for diseases. Something that could also probably be really cool in a Sigler novel.

    Hadn’t heard of this though. Interesting. I just might have to visit those links… xD

    "Urban legends go well with parmesan and horror. In fact their name is conveniently one and the same: Stevie." {UNdead GirlCo Knight for Sigler}

    Profile photo of Beth_Ailis

    Saw this NOVA episode last night and I thought it was very intriguing. I’m sure that some of the more scienticifally inclined Junkies and FDO have already heard about this, but it’s totally cool. Lots of experiments with identical twins where one has a disease/disorder and the other doesn’t.

    I particularly thought that the study based on the community in Sweden was interesting. Basically that there was a strong correlation between what the grandparents experienced (famine or plenty) and the life expectancy of their grandchildren — implying that environmental exposure and damage to past generations may have effects way down the link on the epigenetics of future generations.

    Here are your links:

    http://www.pbs.org/wgbh/nova/genes/issa.html

    http://www.pbs.org/wgbh/nova/sciencenow/3411/02.html (watch the show)

    http://www.livescience.com/health/050708_identical_twins.html

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