How to extract DNA from strawberries


Hi, I am Dr. Eric Green. I am the director
of the National Human Genome Research Institute, at the National Institutes of Health. I am
here with my wonderful side-kick. I am Dr. Carla Easter, also at the National
Human Genome Research Institute, at the National Institutes of Health. And I am the education
specialist. And today we’re here to — Isolate strawberry DNA using household things,
I guess. Basically, we are going to show you how to get DNA out of a strawberry. Okay, great. And why do we pick strawberries? Well, for me there are many reasons. But first
of all they smell really nice. They’re very pretty. The other thing is that they’re nice
and edible. And their seeds are on the outside of the strawberry. And I have found that it’s
very easy to get DNA out of a strawberry. Although of course, like all living things,
they have DNA. We could pick a variety of different, other things to purify DNA from.
We just picked strawberries because it’s easy and they’re easy to get. There we go. So — Okay. You ready to start? Yep. What do we do? So the first thing we’re going to do is take
our frozen strawberries, you notice they don’t look like — And they’re a little different than that. — those nice strawberries. Yeah, right. And we’re going to place them in this plastic
bag. And now you can purify DNA from these strawberries
or these. Oh, certainly. We just picked frozen ones because they’re
squooshier and mooshier, right? Yes. And we’re going to — And you can get them anytime of the year. Okay. So we’re putting them here in the plastic
bag. Yep. And the reason we’re doing that is because
the first thing we need to do is bust them open. That’s right. That’s right. And the reason for that is that the DNA is
inside the cells in that strawberry. And we got that DNA to sort of go into solution,
so that we can purify it. Excellent. So we do this and I am going to smash them
and I am going to point this towards you — [laughter] — just in case it breaks open, but I know
my job here is just to — — smash them all up. Smash them up. Excellent. So while Dr. Green is smashing,
I am going to make what’s called a lysis solution. Lysis? Lysis. What does lysis mean? So lysis means to break open. And the purpose
of the lysis solution is to break open the strawberries cells to get to the DNA, which
as Dr. Green said, is inside the strawberries. And a cell is just basically a bag of living
materials and living different kinds of molecules surrounded by a membrane; sort of think of
like Saran wrap, or we could think of it actually like a water balloon. And we need — inside
instead of water — there actually is water, but in there is also DNA. And we’re going
to use a solution to bust open these cells, or bust up these teeny, teeny, little, water
balloons. Excellent. So we’re going to use household
chemicals, as we said, at the beginning. This is just regular detergent. Just like for cleaning dishes. Exactly. Or you could use hand soap or shampoo.
Works really well. So two teaspoons of detergent. We’re going to take a half of teaspoon of
salt, and then we’re going to add half a cup of water. Okay. And I am going to stir this up. Okay, I think the strawberry puree is — Is all ready? — is ready to go. Perfect. So here we go. Detergent and the salt together
are just going to bust open those little cells, those little water balloons. I am going to
do this. I know I am not supposed to pound on it anymore — That’s right. — otherwise we actually will get a shower. There we go. With soap and all. So the point is you don’t want to create a
lot of bubbles as your mixing the lysis solution around with your strawberry puree. Otherwise, you just have a bubble bath. That’s right. Okay, so we’re just — [inaudible] — I can hear the water balloons just busting
out from the sides. Can you hear that DNA coming out? It is and it’s saying, “I am free, I am
free, I am liberated, I am in the solution now.” Excellent. But now we have all bits and pieces of strawberries
mixed in with all this liquid. So that’s probably a little bit too ooky for what we need to
do. Exactly. It would be very hard for us to see
the DNA in this mess that we’ve created. Right. So what we’re going to do is filter it. And
as you can see I am using just a regular coffee filter. Just one that you would use for making
coffee at home in a coffee maker. And — And it’s just going to pull out, separate
out the liquid from the strawberry guck. Guck is technical term we use here in genetics. That’s right, all the time. So I am going to pour. Good. We don’t actually need all of it, we just
need a good amount, right? Exactly. And what I am going to do is just
fold the edges up, and make just a small little sac; and this just makes it easier to push
the DNA that’s in the liquid away from the big pieces of strawberry. And you want to
be gentle. You don’t want to squeeze so hard that you actually break the filter, otherwise
— The guck — — the guck will go back in there. Just like coffee grounds that would just get
in your coffee. Exactly. Okay, does that look good? Looks good. Perfect. Alright so this is basically the material
that was in the cells of the strawberry. [assent] And it has lots and lots and lots of different
kinds of chemicals in there, because all the contents of a strawberry cell. But the good
news is that a lot of DNA should be there because strawberries have a lot of DNA. Yep. And so we need to get the DNA out of solution
because it’s now dissolved — Right. — in the detergent. So we’re going to do what’s called, “precipitation.” Okay. Precipitation. Precipitation. So, it’s going to rain? It’s going to rain. Okay. Basically. All right. So when you think about precipitation in this
case, hopefully, if we’ve done this right the DNA will fall out of solution. We’ll actually
get to see the DNA start to form. Just as the rain comes out of the clouds or the snow,
we’ll see DNA start to form in our solution here. Or in science, or in particular in chemistry,
when you talk about precipitation, it’s often about something that’s in solution becoming
solid again, or becoming material that you could then see, and then manipulate not in
a liquid form. And so we’re going to try to get the DNA to come out of solution. Excellent. So to do that, what do we do? We’re going to use just regular rubbing alcohol.
Just any old rubbing alcohol that you would buy at any old drugstore. Right. Okay. And this is not the alcohol you drink. Nope, certainly not. And we’re just going to pour an equal amount, right — [assent] That’s right. — to the strawberry juice, if you will. So
I’ll just carefully pour. Stop about there. Perfect. And what you immediately see, of course, is
almost like two different layers forming. Exactly. So you can see two different, sort
of, phases. So you have all that red stuff that’s at the bottom, and then we’ve got something
that’s forming up here in the top. Slimy, gunky, gross. Almost like snot — [laughter] — or a cotton ball. Sort of cotton ball in
liquid. Excellent. It’s interesting is that the redness of the
strawberry is not, and the upper layer, it’s in the lower layer. And so what’s the gunky,
slimy, stuff. I don’t know. I think it’s the DNA. [laughter] What do you think it is? I remember in medical school — [inaudible] — you know in medical school
— we started with strawberries and we learned strawberry medicine. And here we go. Awesome. So, yeah. So you can sort of see the DNA precipitating
— Precipitating. — coming out of solution into a solid form,
and there’s a lot of it. Awesome. So you can see that nicely. So I guess we
can use something and we just happen to here a popsicle sticks — [assent] — a little bit notched to go in. And we can
just touch it. And very easily pick it up. Looks like just a — That’s awesome. — big, old, slimy, wad of strawberry DNA. That’s awesome. Now that you have it, you have it separated.
This is purifying DNA. And actually what’s amazing is that is has no red with it at all.
It’s just totally white, which is exactly what DNA should be. What could you do with
this after you’ve done it? So I always tell the students when I am doing
this in the classroom that, first of all this is extremely dirty, so if we were going to
do any sort of experimentation we would want to clean it up. But one of the things you
could do is actually analyze this DNA. So just as you would watch CSI or any of those
other forensic shows, this is the same way they would isolate DNA from skin, or from
blood, or anything just using different chemicals. So the opportunity would be to now analyze
it and sort of figure out what is it? Where’s it from? Now so this of course is strawberry DNA, but
in hospitals increasingly now we’re purifying DNA from blood, or form scrapes from inside
of your cheek and doing all sorts of medical tests. And that, in many ways, is the future
of medicine. Is looking at humans’ DNA and trying to figure out thing about it that may
be relevant for your health. Now for students at home who actually do this, can they same
this DNA? Of course. How would they do that? Actually you can put it into a sealed container
and put it in the refrigerator and it would stay for a long time. Like a zip-lock bag or — Like a zip-lock bag — –something like that — — or a small tube — –little container. — as long as you could seal it up. Okay. So if they want to do this at home.
What do they — how do they get instructions — So if you wanted to do this — — to figure out how to do it? — you can visit our website and just go and
look at the instructions and do exactly what Dr. Green and I did here and isolate your
own strawberry DNA. And we have point-by-point, tell them exactly
what to do — Exactly. Those instructions are on our website. Well,
that’s great. Okay. So this was wonderful. Thanks for helping me do this. Thank you. And I hope everybody enjoyed it.

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