I think the key there will be making sure that all the straws are
exactly the same length -- each straw behaves like a resistor, so just
like any other resistive material, a greater amount of material will
mean a higher resistance (and thus lower current at constant voltage).
> How do you stain for DNA in a straw? All the protocols I used (again,
> 10 years ago) involved staining the gel after a run.
Easiest way to do that would be to use a stain that you add to the
warm agarose before pouring, such as SYBR Safe or GR Safe (or ethidium
bromide, but the cool kids don't use that anymore).
I suppose you could slit the straw open with a razor blade if you
wanted to use methylene blue, but that sounds like a huge pain in the
We could of course find out for sure by doing a bunch of test runs of
nothing but molecular weight markers.
There's also the option of working on the optics-based solutions :-).
But at the moment, if you have stains laying around, it's easier to stain.
here's another idea:
Before filling the straw with gel, place a smaller straw inside and well
centered. Load the DNA into the ring-shaped cavity between the walls.
Then, when you want to stain, just pull the inner straw out and suck
methylene blue into the empty "core".
Oooh, good one! Though safety concerns prompt me to issue the
reminder, never pipet by mouth. (There are squeezy-bulb things that
will do the job just fine.)
A bubble-tea straw and a regular straw would do the job, I think. Toric gels!
To make it show up you have to stain it with some chemical, then
usually illuminate it with a certain wavelength. The traditional way
is to stain w/ ethidium bromide, then view it with UV. Now days there
are other, more expensive, chemicals (SYBR Green, SYBR Gold, SYBR
Safe, etc). Here is a gel I ran today. The gel was pre-stained with
ethidium bromide, illuminated w/ UV-B...
> Do I just
> spit in the little hole that I put the food coloring in before? :)
You'd probably want to purify the DNA from the mucus and cells. A
while back I think someone posted a simple protocol for doing a crude
dna purification from spit. Maybe try that? Else, in anti-DIY
fashion, you could buy some. I usually use NEB's 1kb ladder (
http://www.neb.com/nebecomm/products/productN3232.asp ). That is what
I used in the picture I posted, far left lane.
> DIY BIO ROCKS! Tell me more things I can try! Can I like take the dna and
> apply pcr to it? How do I do that etc... ?
Sure. You have to purify the DNA from the gel first. I haven't seen
any DIY protocols for this yet. The most widely used one these days
is Qiagen's gel extraction kit (
http://www1.qiagen.com/Products/DnaCleanup/GelCleanup.aspx ). The DNA
eluted in this protocol can be used directly in PCR.
> Easiest way to do that would be to use a stain that you add to the
> warm agarose before pouring, such as SYBR Safe or GR Safe (or ethidium
> bromide, but the cool kids don't use that anymore).
I wouldn't recommend adding the SYBR dyes directly to the molten
agarose. From what I have tested, both SYBR Green and SYBR Gold slow
down the migration of the bands. It may be a linear effect, but I
haven't made any precise measurements. I just stick to poststaining
w/ the SYBRs. Oh, and by the way, the cool kids _do_ still use
ethidium ;-) Its cheap, bright, and there is no problem adding it to
the agarose prior to casting.
Also, I noticed the protocol used for this food-coloring separation
uses regular agar. If anyone has good results separating DNA with
agar, please tell me. Agar is so much cheaper than agarose.
So if your ladder had a 2kb band and your sample had a 2kb band, how
could you tell that your sample had any DNA in it? The bands would be
in the sample place. Plus, if you wanted to purify your band, you
would end up with the ladder in there as well.
this is stupid. just run the straws in the same chamber with the same
electrodes from the same batch of agarose at different times. think
"gel spectrometer calibration" not "horse race"