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Home DNA Sequencing
An anonymous reader writes "Wired is running an article about high-tech gifts for Christmas, including a home DNA sequencing kit targeted at kids for under $100. What's next, the Fisher Price Cloning kit?"
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Why pay when you can do it for free?
Unfortunately, this is a bit far from sequencing. All you're doing is taking the raw DNA and making it insoluble in water. So, really, it's a great way to make false snot... which should appeal to the young male sector more anyway. Gross is G00d
It doesn't work too well, when you light the ring, it doesn't ignite evenly, it just sorta flashes upward from the point where you ignited it, no flaming rings shooting across the room, as cool as that would be.
"Sic Semper Tyrannosaurus Rex."
I'm curious as to what they're using for staining - the gold standard in the lab is ethidium bromide. However, I'm certain that isn't in the kit - it is a very powerful mutagen.
Cyber Green? I think that's fairly safe.... Ethidium Bromide would be bad!
Would have been nice if they could have included some cheap and robust restriction enzyme, to produce fingerprints. However this would then require hybridisation with a probe to bring out a few bands - way too complex/expensive. Anyone think of a cheaper and easier way of producing a nice fingerprint? It would be good to have a Mark II kit that actually did something usefull...
Its not quite what it says on the story, its not DNA sequencing its just a DNA seperation kit using the bog standard ethanol prep which you can do with washing up liquid, salt and a bottle of (80%) Polish vodka. The electrophoresis step is quite nice using a battery to provide the DC current. However the kit is nothing you could not make yourself (Most of Molecular biology is really quite low tech the main requirement is getting pure reagents to do it with)
Thats not to say its not a cool gift/toy, at the very least the Centrifuge, and Electrophoresis chamber could probably be reused by the budding geekling
here is the link to the actual product.
It's just gene mapping via electrophoresis, rather than sequencing. The stuff to do it crudely is actually pretty simple and cheap.
All it gets you is a pattern of sites that the enzymes cut at, not a sequence. Still, this is how a lot of DNA work (particularly forensics) is done, and it's awesome enough for me to want one (even though I have ready access to the real stuff).
Well it will never give you a full dna report as you need to do more than just a simple gell. I am curious as to what the enzymes are. My guess is that they are specific for certain base patterns and cut the DNA into smaller pieces. (Alternatives they could be peptiases and just eat up the protein from the peas) The smaller pieces will transverse the gell faster than the larger pieces. So while the experiment will detect DNA all it will be able to report on is how many pieces of DNA you can create with the enzymes. Of course, if you do not know the enzyme, even this info will be useless.
I make my face look like this and concerned words come out.
Quite simply there is no sequencing ocurring. It's merely separation of DNA molecules. This will just tell you their size. There's not sufficient information in the article or the store blurb for me to figure out if restriction enzymes are being included, which would make things slightly more interesting. In the days before PCR and DNA sequencing was as easy as it is now, genetic tests were done via Restriction Fragment Length Polymorphisms, so your DNA would break up into differently sized bits depending on which sequence was present at a cutting site.
I took a little time to read the description of the kit on Discovery's website. It's much less than the /. post suggested. There's just some chemicals and a toy centrifuge to extract DNA. Actually there are ways to extract DNA with household chemicals, precipitate with isopropanol and spool on a glass or plastic rod.
So far it's only DNA extraction, cool as a science-for-fun thing, but nothing new.
The analysis part (with electrophoresis) seems to be fake (simulated, if you wish). The kit, according to the Discovery website contains
"DNA stain (fabricated to mimic real DNA)".
So, it's just a toy, cool, but nothing that'll allow Junior to test his paternity or do any real DNA analysis. There are educational kits that provide real DNA analysis in a classroom environment (like the Biotechnology Explorer program from BioRad), but they still require teacher's supervision.
Sorry, the poster and Wired got it wrong. The original source calls this a gene mapper. That probably means it includes restriction enzymes for cutting the DNA into chuncks. This is not the same as finding the primary sequence. Sequencing by all current common methods requires either radioactivity or a fluorescent laser detection device. Neither of which is likely to be provided for $80. (Or I'd buy it for my lab!!)
over atx ?language=en-GB&product=DNATIN&category=LIFE
www.iwoot.com
you can get a different but more professional dna in a tin kit
http://www.iwantoneofthose.com/ProductDetails.asp
its not DIY though, its a mail in DNA kit
*resistance is futile, or fuzzy, i dunno*
You also get to do electrophoresis and take pictures of your product, which is kinda cool. I can just see what's going throuh those kids minds right now....So, how similar are fido and the cat? What if I compare little sister's DNA to mine? Hey, you hold down the dog while I get some blood....oops....
There is a reason for everything. Sometimes that reason just sucks.
Well, it's a fair question, and to some degree it's difficult to answer, because ... well, at this point, a lot of DNA sequence information is kind of like Bernoulli's law before airplanes, or the rules of Boolean algebra before computers. IOW, we know that there's a lot we can do with the information, but we haven't actually built the machines yet.
That being said, there's a lot of useful work going on with at least some DNA sequence information right now. Here (as a comp. bio. grad student) are the ones I can think of at the moment:
- Microbial and viral sequence data is probably the most immediately useful, because by comparing the sequences of different strains of pathogens (e.g. HIV) we can track the emergence of these strains, figure out when and where they originated, and hopefully control the most virulent strains.
- More excitingly, these little critters tend to have genomes that are really simple; learning, e.g., which genes in a viral genome code for which proteins in its coat allows us to develop new drugs against it. AFAIK, most of the latest generation of AIDS drugs (which don't cure the disease, certainly, but do allow its victims to live much longer and better lives than previously) were developed this way.
- In a similar vein to the first item, it's possible to track the evolutionary development of bigger organisms (e.g., us) by comparing changes in sequences between those organisms and their close relatives (e.g., other primates). This kind of "phylogenetics" has already changed a lot of previous assumptions about various organisms' relationships to each other and their common ancestors; it's not an exaggeration to say it's redrawing our picture of the tree of life. This is, of course, pure science rather than engineering; whether you value knowledge for its own sake is up to you. (And if you're a creationist, then please stop reading; I don't like spending my time explaining things to idiots.;)
- "Bad" gene sequences are the cause of cancer, and of almost every other non-infectious disease we know of. (Sickle-cell, cystic fibrosis, Tay-Sachs, you name it.) Right now, about all we can do is identify individuals who are at higher risk for some form of cancer because of some particular kink in their DNA. That's still important, because it allows those individuals to be more closely tracked and given earlier treatment if and when tumours do appear. However
... - We are at the dawn of the gene therapy era. (Like all ages of exploration, it's risky; so far I think the score is something like two patients cured, twenty killed.) It is entirely reasonable to expect that within a decade or two, we will be able to insert "good" copies of "bad" genes, replacing the genes which cause these diseases. This is the whiz-bang stuff that has everyone so excited.
There's plenty more, but this is the stuff I can come up with off the top of my head and with only half a cup of coffee so far this morning.The correlation between ignorance of statistics and using "correlation is not causation" as an argument is close to 1.
And I'm pretty sure it intercolates as well (it only interacts with dsDNA), so it's a potential mutagen. Not proven, but still not up for handing out to kids.
I was just showing that to a labmate, and we think that it could simply be hemotoxylin (sp? I never write it out..as in H&E). It's purple, and since the gel should be fairly devoid of protein, it should specifically stain DNA.
There is a reason for everything. Sometimes that reason just sucks.
No I'm a molecular biologist I mean 80% by volume (160 proof) anything much less won't precipitate the DNA. I'm in the UK and can buy 80% vodka from my local supermarket. (I plan to buy a bottle and use it when doing demos for the university open day .... granted I'll empty the bottle and use the lab ethanol, but the appearance that counts.)
A little Googling gives me a 160 proof spirit Polmos Polish Pure Spirit (about half way down the page). Technically it may not be a vodka, in my travels I read the a vodka has to be between 80 and 110 by proof (OTOH my brain cells will probably not make the distinction:-). I also came across references that booze above 140 proof was illegal to sell in the US
Another poster gave a good explanation of the applications of sequencing. I'll give you a quick explanation of how it is done:
...
1. Obtain a pure sample of DNA to sequence. You have to know a little bit of the sequence at the start (not a problem - when you sequence an unknown DNA sample you usually chop it up into bite-sized chunks and insert them into bits of bacterial DNA to make lots of copies of them - this means the unknown DNA has bacterial DNA on either end of it and you already know the sequence of that part).
2. Make a short strand of DNA that binds to the known portion of DNA sequence at the start of unknown portion. These are called primers.
3. Mix the DNA to be sequenced with the primers, heat them up and cool them. This results in long pieces of uknown DNA with the primers stuck to the beginning.
4. Throw in the building blocks of DNA - but a small portion of them are essentially defective and marked with fluorescent tags.
5. Throw in DNA replicating enzymes - these guys look for primers and try to copy the unknown DNA starting at the side of the DNA with the primers attached.
The DNA replicating enzymes will copy the DNA until they accidentally grab a building-block which is defective (which happens a small portion of the time - since most of the building blocks in the mixture work fine). At that point the defective building block is attached to the end of the DNA strand and that strand cannot be copied further.
At the end you end up with a mix of DNA strands that look like:
1. Only one step of the DNA ladder copied - because the first block grabbed was defective.
2. Only two steps copied - the second block was defective.
3. Three blocks copied.
N. The whole strand is copied.
Each of these DNA strands is one step longer than the strand before it. Each has a fluorescent tag at the end - since each ends with a defective block.
You then put this mix of partial strands onto a gel and apply an electrical current - the bigger strands move through the gel more slowly (they get stuck in the pores in the gel).
You end up with a gel with a long ladder-like series of bands - each band is a DNA strand one step longer than the band before it. Each is fluorescently tagged.
Now here is the magic - back when you put the defective building blocks in you actually used a mixture of four blocks (the four types of steps in DNA) each with a different color tag on it. So each band is a different color - corresponding to the color of the last step that was added to the chain. The pattern of colors corresponds to the sequence of the DNA.
I tried to simplify this explanation for those with only a basic understanding of biochemistry. There are various ways of doing DNA sequencing, and these days much of it is automated.
Oh - where the computers come in is this:
A gel like the one I described can only handle pieces of DNA up to about 400 steps long. That means that you can only sequence 400 bases at a time (a base is a step in the DNA ladder). A human being has 4 billion bases in their DNA.
The way you sequence the whole human genome is to chop it up into lots of 400 base units. You actually take lots of copies of the human genome and chop it into lots of random pieces. Then you sequence pieces until you're sequenced about 40 billion bases. Then you have a computer run through the sequences looking for overlaps. The computer will find lots of regions that are sequenced several times, and some regions that weren't sequenced at all. However, it will give you a pretty good sequence of the overall genome, and then some careful followup work can fill in the gaps (the followup work is less easily automated, so they try to get most of it using the random method).
Historically they separated digested DNA fragments on a gel which was big enough to view with the naked eye. I would expect now that they use capillary electrophoresis hooked up to an optical detector. DNA absorbs UV light, or they may attach a fluorescent probe, that's how sequencing machines do it. DNA fingerprinting is VERY good technology, and does not rely on humans making a judgement call. It's not perfect though, sample handling is extremely important.
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