h a l f b a k e r yI think, therefore I am thinking.
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How big are these DNA? Or are they magnified by an
extra, extra thick glass? I'll bun if you explain. |
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Yes - what do you actually see? DNA in solution will look
like water. You could have a few globs floating around in
ethanol, but that'll just look as if somebody sneezed (or
worse) into your snowglobe. |
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//store some of yours or your family members' DNA for the future// |
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Erm, isn't that reproduction is supposed to do? |
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Well, I read that you could use a piece of hair or something simple as a DNA sample. I'm not a scientist, so if you want a scientific explanation...I don't really know. I'm a halfbaker! |
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[MB] What you see are the objects you pick to put in the snowglobe- like a double helix, floating particles, etc. |
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Doesn't anyone have an imagination, or should I be more specific in my description? |
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halfbakery: imagination confused |
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//I'm not a scientist, so if you want a scientific
explanation...I don't really know.// |
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Yeah, but, just because DNA is a cool acronym doth
not an idea make. How about a snowglobe that
indicates your financial liquidity? I'm not an
economist but... |
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I resent that comment [MB]. I know very well what DNA is and I know what snowglobes are. I see no reason why this is not an idea. If you don't like it that's fine, but if you just don't like me, well then... |
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I think this idea is fine; it's basically a snowglobe as commonly known, but with DNA in the water, right? Only the proportions of the thing's components need some modification. If the globe and decorative pieces were microscopic, could the DNA not serve as the glitter (or whatever else is floating in traditional snowglobes)? It would need to be viewed under a microscope, but it brings christmas to the genetics lab worker, right? And it would be best if the DNA were in chromosomal bunches, so they might look like this: + |
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[xan] it's nothing personal, it's the idea. It's just
that, as posted, there's no obvious way to
"present" the DNA, or make the end result look in
any way different from a regular snowglobe. |
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Now, if you'd said something like "use ingeniously
magnetized glitter bearing the letters A,C G and
T, which will spontaneously assemble into a short
sequence"; or "include a full diploid set of plastic
chromosomes, with red bars representing harmful
mutations, from both you and your partner, so
that when you shake the globe you get a random
segregation and can tell whether your offspring
will be colourblind"; or "fill the globe with about
30% ethanol instead of water, so that the DNA
precipitates to form snowflakes when put in the
fridge, but redissolves in a warm room" or.... |
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I think it just needed more more. |
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Not all of us are so eloquent, besides I posted at 5 am, but thank you.
Can I hire you to write up my ideas? At least you admitted it WAS an idea! |
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I like it as it is - decorated by yourself as a kind of time capsule. Tsk, some bakers... |
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//eloquent// Sp. enebriated |
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DNA precipitated with ethanol looks a bit like clouds. |
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So why not call it a skyglobe or similar, and you're fine. |
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If you just want DNA, it's fairly easily extracted in bulk from onions.
If you want it to be your own DNA - and enough to be visible - then you'll either need a larger sample than a hair follicle, or do some replication (PCR or perhaps HDA). |
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Either way, I don't think it would be ready within an hour. |
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A ml of blood will give you a decent glob of the
stuff, enough for maybe three or four snowflake-
sized snowflakes as a precipitate in ethanol. |
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You'd need more blood ("why, that's very nearly an
armful!") to make a really dense blizzard. |
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Plus, you might find that precipitated DNA would
glob together, giving you something that looked
intermediate between a snowball and a jellyfish. |
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Even taking a pinprick of blood would probably necessitate biohazard precautions.
Drawing more blood than that (probably even that) would limit the market to a few non-squeamish geeks. |
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Much easier to take a hair follicle and copy up to what is needed - although then again, the economics of that might be a bit steep. |
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You could use one of the new isothermal random-
primed kits, which basically amplify up whatever you
throw in, and don't need a thermocycler. Kits run at
a few dollars per sample or less, although the "real"
price of the components is pence. |
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There are other sources of abundant DNA which do
not require bleeding, although it will reduce your
client base by 50%. |
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A jellyfish globe would be pretty cool. You know this is a //poorly thought out idea// as [jutta] states what the hb is... |
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//You could use one of the new isothermal random- primed kits, which basically amplify up whatever you throw in, and don't need a thermocycler.// |
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That's what I was thinking. Until I saw the kit price and yield.
I suppose you might be able to do a deal with the manufacturer to get much larger kits suitable for the service. They'd be worried about them getting split up and sold on, though - which would totally cannibalise their business. Could try selling it to them as a PR exercise I suppose. |
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[MB] //50%// Not in China. |
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If you bought the ingredients rather than the kit,
and particularly if you bought the polymerase from
some dodgy supplier, you could do it for pence per
person - maybe a dollar at most. |
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Get a mosquito to bite you and then encase it in
amber. Future scientists will then clone and exhibit
you. |
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Well, no two people are genetically identical (and
yes, that includes identical twins). In fact, no two
cells in your body have the same genome, but don't
tell everyone or the money will fall right out of
'genomic medicine'. |
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//If you bought the ingredients rather than the kit, and particularly if you bought the polymerase from some dodgy supplier, you could do it for pence per person - maybe a dollar at most.// |
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Polymerase, helicase, dNTPs ... how much DNA do we want again? |
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//In fact, no two cells in your body have the same genome// |
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Human (diploid) genome : ~=6 billion bp = 6,000,000,000 |
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Mammalian error rate : ~10^-8 per bp. |
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Average number of errors per genome replication (product of above two numbers) : 60 |
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Number of cells in human body (order of magnitude) : 10^14 |
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Poission distribution with above values: |
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f(0;60)=60^0 x e^(-60) / 0! = e^(-60) = 8.76 x 10^-27 |
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so naively you might be right. |
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However, your imprecise wording makes me still want to try and take you up on that as a bet. |
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Your mammalian error rate is the wrong one. By far
the commonest changes are copy-number changes
(loss or gain of segments). Huge swathes of cells
have extra (or missing) chunks of genome. Not only
that but (I predict) some of these inter-cell, intra-
organismal changes will be regulatory in nature (eg,
the best way to shut down a gene for good is to just
lose it). |
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//Your mammalian error rate is the wrong one.// |
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Doesn't matter - it still comes out as extremely unlikely that any pair of daughter cells are identical in a human organism. |
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//By far the commonest changes are copy-number changes (loss or gain of segments). Huge swathes of cells have extra (or missing) chunks of genome. Not only that but (I predict) some of these inter-cell, intra- organismal changes will be regulatory in nature (eg, the best way to shut down a gene for good is to just lose it).// |
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Absolutely. Human red blood cells are anucleate and mitochondrea-free, so they all have the same genetic content (absolutely none at all; a 'null' genome). This is why I'd win the bet. |
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Out of interest, what sort of error rate are we talking for chromosomal mis-assignment or indels in mitosis? |
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And regarding intra-organism regulation by genetic rearrangement, I only know of the immune system in 'higher' eukaryotes.
In prokaryotes and small eukaryotes on the other hand, I know of quite a few such systems ranging from simple switches to the really quite involved (such as how the malaria parasite evades the immune system). There's also a beautiful mechanism for detecting plasmid dimers, and a mechanism by which transposons direct reintegration.
So there are basically two themes: generation of diversity, and detection of genome structure. |
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I do vaguely remember that some small multicellular organisms delete parts of their genome in certain specific cells, so that may happen in humans, although I haven't heard of it specifically (besides complete annucleation as in red blood cells, of course).
I'd be really quite interested if you could say more about that. |
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//what sort of error rate are we talking for
chromosomal mis-assignment or indels in
mitosis// |
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I don't think anyone knows, really, because almost
all of genomics is based on the assumption that all
the cells in one person are clonal, and that their
white blood cells are the same as any other (apart
from some fancy stuff going on in immunoglobulin
genes). I'm talking here about copy-number
changes involving segments of chromosomes, not
aneuploidies which involve extra or missing whole
chromosomes, although somatic aneuploidies are
known and are probably commoner than believed. |
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One guy looked at genomic differences between
different tissues of the same (dead) person; in
each of several people, he found copy-number
differences between different tissues. Each
tissue sample consisted of many thousands of
cells, so it's likely that he only saw differences
which arose in the first few cell divisions during
development and hence affected large
subpopulations of cells; later changes would
affect only a smaller number of cells and would
have been averaged out in his samples. If we
assume that such
events occur equally in all mitoses, then it's very
unlikely that any cell in an adult retains the
original genome, even without the point-mutation
errors you alluded to. |
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People have done other stuff, such as comparing
identical twins (again, they find differences), but
it's really only beginning to dawn on people that
this variation is significant and abundant. |
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My guess is that (a) some genomic changes will be
programmed (cells use every other trick to
regulate genes) and (b) a fair proportion of
diseases will turn out to be due to these somatic
copy-number changes. |
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Just reading the title, before I even opened the post, gave
me the mental image of a snowglobe filled with flakes of
dead skin. Thanks for that. |
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You're thinking of the Dandruff Snowglobe. Also DIY. |
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What does [21 Quest]'s head have to do with this? |
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