Dna

Discussion in 'Off-Topic' started by Ziggy Stardust, Jan 22, 2013.

  1. Ziggy Stardust

    Ziggy Stardust New Englander

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    edit: bloody title won't bloody accept bloody all-caps.

    So, DNA.

    I just realized I knew very little of the stuff. I realize you can use it to tell whether someone is susceptible to a particular disease. But what else can you do with it that I'm unaware off.

    What can we determine from it? Does it tell of my ancestors? Can you use it to tell what I had for lunch? What other conclusions can be drawn from DNA?
     
  2. Gigaz

    Gigaz civoholic

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    From your DNA it is usually possible to tell much about one's ancestry up to the point that for Non-Americans it yields good information about the place where the person is born.
    You could propably get a good guess about someone's skin color, but you can not reconstruct a picture of the person from his DNA with today's methods. (From identical twins it is known that the overall appearance of a person is mostly determined from his or her DNA, but its much more complicated than "gene A - blue eyes, gene B - blond hair". The outcome depends on the interplay of all genes)
    A persons intelligence depends so much on the environment that conclusions from the genes give no good results.
     
  3. Borachio

    Borachio Way past lunacy

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    Isn't mitochondrial DNA the one for ancestry?

    And is that passed down through the female line unmutated?
     
  4. Ziggy Stardust

    Ziggy Stardust New Englander

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    Thanks Gigz. You told me at least 2 things I didn't know.

    Now I'm off, googling 'mitochondrial'.
     
  5. Ziggy Stardust

    Ziggy Stardust New Englander

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    http://en.wikipedia.org/wiki/Mitochondrial_DNA

     
  6. El_Machinae

    El_Machinae Colour vision since 2018 Retired Moderator

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    So, I heartily recommend people pick up some equivalent of Genetics for Dummies, as I explain in this thread. You could become a resource for every single friend and loved one.

    Mitochondria are best thought of as bacteria inside each of your cells. They're partially independent organisms and they are what help turn food into usable energy. They're like the British Petroleum of the cell: crude fuels go in, refined fuel comes out and then is used by the rest of the cell's infrastructure.

    These mitochondria themselves have genomes, and these genomes help encode genes for necessary mitochondrial function. They replicate and divide themselves. Obviously, their genomes are not kept in the same place as the 'main' store of DNA in your cells (which is the nucleus). So, when your mom creates an egg with half of her genes and your dad makes a sperm with half his genes, the egg has mitochondria in it (mainly because it's so relatively big).

    When the sperm hits the egg, they fuse, and so the two groups of genes mix to form a 'human' genome. The mitochondria, though, are mostly from the egg and so those "bacteria" go on to divide and replicate as the embryo turns multicellular. Each cell then has the two (mixed) human genomes and the mito DNA (mtDNA) that came from the egg.
     
  7. Ziggy Stardust

    Ziggy Stardust New Englander

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    Thanks for the link, at work at the mo' but will check when I get home.

    (And thanks for the extra info on the Mitochondria Mystery)
     
  8. illram

    illram Deity Retired Moderator

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  9. MagisterCultuum

    MagisterCultuum Great Sage

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    Mitochondrial DNA still mutates, but it does so at a slow, fairly predictable rate.

    It used to be thought that Mitochondrial DNA could come only from the egg, but it is now believed that the mitochondria from the sperm can survive and contribute to the Mitochondrial DNA of the offspring too.

    However, the human egg is vastly larger than the human sperm and contain vastly greater numbers of mitochondria. This dilutes the father's contribution to the point that it is typically less significant than the changes that arise from random mutations.

    Mitochondrial DNA is still a good way to track the maternal line.



    The paternal line of males can also be traced, using the Y-Chromosome. Females do not have this chromosome, so it is passed down from father to son as unchanged as mitochondrial DNA is passed from mother to child. It can still mutate slowly and it is not completely impossible from certain genes to cross over to or from an X-chromosome, but is stays the same well enough to trace.


    If I recall correctly, there is a very distinctive Y-Chromosome mutation that is pretty good at identifying Jewish communities. Not all Jewish men have it (perhaps because converts and those born to a Jewish mother and gentile father are still considered Jews), but it is common among Jews in general and almost universal among those claiming to be Kohenim. (To qualify as a Kohen, a man must not only have a Jewish mother but must also be descended through an unbroken paternal line all the way back to Aaron, the brother of Moses and first High Priest of Israel.) Not everyone who has the gene is Jewish either though. If I remember correctly, it is also relatively common among Arabs and French Canadians.
     
  10. Part_Time_Civer

    Part_Time_Civer Warlord

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    So does this mean that we actually have some of our father's mitochondrial DNA? If so, can daughters transfer their fathers' mitochondrial DNA to their children?
     
  11. Terxpahseyton

    Terxpahseyton One. And many.

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    What I find the most fascinating aspect of DNA is how environmental inputs can cause different parts of it to be activated and deactivated.
    There for instance was a study with the ancestors of Dutch women who had to starve during WWII and the starving modified their DNA in a way bad for the health. And this modification was passed down to the next generations, but in the process, the by starving induced modification also weakened with each generation.
    But it isn't just such extreme cases, of course. Ones lifestyle will influence what genes are activated and which are not. And how you life your life will have sway what genes in your kids will tend to be activated and which won't.
    In a nutshell: DNA adapts in its effects to the environment and we inherit that adaption.
     
  12. El_Machinae

    El_Machinae Colour vision since 2018 Retired Moderator

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    How does DNA work?

    Imagine that you want to bake a cake, and the recipe is online. What do you do?

    Well, you look up the recipe online, then you print out the recipe, and then you use the recipe to bake the cake ... delicious!



    There is machinery in every cell that tries to copy the information in the DNA in a new form. This new form of the information is called RNA.

    There is additional machinery that converts this information into proteins (which are strings of amino acids). The order of the amino acids cause the protein to become a specific shape and that allows the protein to have a specific function. The function of a protein is due to its shape, but its shape is due to the order of the differing amino acids.

    The protein ends up being the dominant 'machinery' in the cells, which tens of thousands of different protein types doing different things. Much like the same metal can become different machine parts (based on its shape), proteins do lots of stuff.
     
  13. Borachio

    Borachio Way past lunacy

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    I heard today that someone has encoded Shakespeare onto DNA to demonstrate, I suppose, how it can be used as an effective long term data store. Since, they said, it can remain uncorrupted for thousands of years, easily enough. And in a very small space.

    So it's easy enough to transcribe digital data into the four base pairs of DNA.

    An experimental and expensive (as yet) technique.
     
  14. ori

    ori Repair Guy Super Moderator

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    I highly doubt the claim that it can remain uncorrupted for thousands of years easily - while storage conditions nowadays either in liquid nitrogen or in a dried state have shown stability for more than a decade - that is a far cry from thousands of years and even then attempts to perform pcr reactions on long term stored dna have had varying success, mostly showing that short fragment pcr is well preserved while long fragment pcr reactions can fail after just a decade or so. Essentially it is quite clear that long term stored dna does degrade DNA after a decade or so at least to some degree. So you would get loss of information through degradation over time.

    Now DNA as such is stable for a long time in that some fragments of it can be found even after thousands of years in suitably preserved specimen - and it might even be possible to piece together a whole genome from those fragments, but there you started out with billions of copies originally so that even the surviving fragments could cover the genome once if you are lucky and are not assured that all read-outs are mutation-free. For information storage however you'll either need redundancy or be able to predict the degradation type.

    Also I do not buy the notion that the got error free readout to start with - they have used both dna synthesis and dna sequencing techniques each of which actually has quite a bit of noise associated with it - so they obviously used redundant information just to tackle the problem that they received noisy data from their readout. (This is from reading reports on the paper - I did not yet have time to actually read it and don't have access to it from home - so they might surprise me right there. Note also that I still regard this as a great idea, I just don't like the overselling of such research ;))
     
  15. Borachio

    Borachio Way past lunacy

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    OK. Thanks for the useful information and insight. It was just something* I heard casually on the radio, so no doubt between the research, the media and me, the idea has become garbled somewhat.


    *And it was a novel idea to me.
     
  16. MrCynical

    MrCynical Deity

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    I've had a look at the paper. They'd designed the DNA strands to be heavily overlapped, resulting in fourfold redundancy for any given base. They actually give rather pessimistic quotes for their DNA synthesis accuracy, but it's not too surprising with that level of redundancy that they could get 100% recovery.

    One interesting bit in the paper is that they can use the actual encoding method to improve the durability of the DNA. For example, the information is encoded in such a way to that there are never more than two identical nucleotides adjacent, which reduces the number of vulnerable sites for DNA damage (such as thymine dimers). I imagine you could also screen out common nuclease cut sites and so on, so these kind of synthetic sequences could be a lot more durable than the kind of natural DNA sequences we normally work with, even under lousy storage conditions. I don't know about thousands of years - maybe if you stored it at liquid nitrogen temperatures a strand would last that long, but there's no real way to tell in a practical amount of time. Looks like its a straightforward trade off - lots of redundancy will preserve the information over extremely long timescales, but at the cost of requiring more DNA strands to store it.
     

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