deoxyribonucleic acid or DNA for short
is the molecule that carries the genetic
information in all living organisms in
terms of structure DNA's a polymer
that's made of four subunits known
simply as AC T and G each of these
subunits has three main components a
unique nitrogenous base a phosphate
group and a sugar they connect together
through their phosphate groups to form
these long polymer chains which are the
basis of DNA the order of the subunits
is extremely important and it's how the
genetic information is stored it gets a
little more complicated though because
DNA isn't just one chain it's actually
two and they're held together by
interactions between the nitrogenous
bases this interaction is known as
hydrogen bonding where a likes to pair
with T and C with G this hydrogen
bonding along with various other
intermolecular forces twists the DNA
into its characteristic ladder-like
structure known as a double helix in
this double stranded system the cell
only reads the information from one
strand and the other is kept as a backup
for example if a mutation occurs and
let's say a c is swapped for an a the
cell can recognize and fix this because
the a wouldn't properly pair with the G
or maybe if some sort of damage occurs
to a large section of one strand the
cell can simply cut it out and rebuild
it based on the other one this is not
how DNA looks in the cell though it's
associated with a whole ton of proteins
that pack it together into a super small
volume it progressively gets packed
tighter and tighter until we eventually
get something called a chromosome which
is the smallest DNA base structure that
you can see under a typical microscope
each chromosome contains a different set
of genes and the number of chromosomes
varies widely among plants and animals
for humans we have 23 pairs of
chromosomes so 46 in total what might be
interesting is that the number of
chromosomes doesn't have any
thing really to do with the
sophistication of the organism for
example a typical potato has 48 so to
more than a human what I think is really
cool is that it's actually possible to
isolate DNA from pretty much any living
thing for this video though I've decided
to get it from strawberries because it's
one of the easiest sources also at the
end once I've isolated the pure DNA I'm
gonna try it out because I'm really
interested to know what it tastes like
anyway
in terms of supplies I'll of course need
some strawberries but I'll also be using
some dish soap non-iodized salt and 99%
isopropyl alcohol before I get started
with the main process there are a couple
things I need to do first the isopropyl
alcohol will be used later on but it
needs to be ice cold so I measure out
about 200 milliliters and then I put it
in the freezer I also need to prepare a
soapy salt solution to do this I mix a
hundred and eighty milliliters of water
20 milliliters of dish soap and about a
teaspoon of salt ideally the soap that's
used is both uncoloured and unscented
but unfortunately I wasn't able to find
this what I ended up using was this red
strawberry scented soap because I
figured both the color and the smell
would be masked by the strawberries the
table salt should also be non-iodized
but it will work if only regular I die
salt is available what we're doing here
is making a so called extraction
solution that we'll be using to get the
DNA out of the cells for now it's going
to be temporarily placed on the side but
when I use it in a few minutes I'll
explain exactly how it works okay with
that other stuff out of the way we can
get started with the actual procedure I
counted out 10 moderately sized
strawberries and then I shoved them all
into a sealable bag one thing I should
mention is that this preparation really
doesn't need gloves and I'm not really
sure why I'm wearing them for it anyway
with all the strawberries in the bag
it's time to squish them
by doing this I'm exposing as many of
the strawberry cells as possible and I'm
also structurally damaging them this
crushing step is really easy to do with
strawberries and it's a major reason why
I'm using them it's common to extract
DNA from other things like chicken liver
or Peas but they don't fall apart nearly
as easily and you often need to use a
blender after a few minutes things
should be adequately broken up so it's
time to add the soapy extraction
solution from before then I mix it
around and try to break up any pieces
that I might have missed it really
doesn't look like much as going on here
but it's actually the most important
step in the extraction which is getting
the DNA out of the cells for plant cells
which strawberries are made of this is
the general anatomy there's a whole
bunch of stuff here that's not relevant
and I really want you to just focus on
the three main things the cell wall the
cell membrane and the nuclear membrane
the cell wall is a rigid sugar layer
that's usually made of cellulose and the
other membranes are made of things
called phospholipids the DNA is stored
in the nucleus so to get to it we need
to destroy all three of these barriers
the first ago was the cell wall which
was broken when I pulverized the
strawberries this exposes the cell
membrane which as I mentioned a second
ago is made of phospholipids the
phospholipids organize themselves into a
bilayer like this where the polar heads
are on the outside and the nonpolar
tails are shielded on the inside soap
itself is very similar to the
phospholipids where it has a polar head
but it only has one nonpolar tail the
structural difference is small but in
water it causes soap to form spherical
structures called micelles instead of
these by layers even though they form
these very different and distinct
structures they're still similar enough
that they want to interact with each
other
when the soap is added it starts
plucking phospholipids and proteins from
the cell membrane and incorporating it
into its
my cells also to some degree the soap
molecules will insert themselves into
the membrane this ultimately leads to
severe damage of the lipid bilayer and
it makes it structurally unstable with
further squashing the membrane bursts
open and the contents of the cell are
spilled out this releases the nuclear
membrane which is the last thing to get
through and it's just like the cell
membrane the soap messes with the lipid
bilayer causing it to burst and the DNA
is released although the cells are just
spitting out DNA we don't actually see
it here because it stays dissolved in
the water
as I mentioned in the intro though the
DNA is tightly packed and associated
with a lot of different proteins many of
the proteins have positive charges which
interact with the negative charges of
the phosphates in DNA this is why we add
the sodium chloride the sodium ion can
come in and displace a lot of these
proteins for me I felt this salt was
good enough but a lot of people also
include some protein enzymes to further
free up the DNA after a few minutes of
squishing I now need to filter off all
the solids strawberry junk
this is done in two steps first through
a strainer to get rid of the really
large pieces and then through a coffee
filter to get rid of the smaller stuff
this part is really slow so it requires
some patience also the filter tends to
get jammed up so I needed to replace it
at least three or four times once
everything passes through though we are
ready to isolate the DNA so to do this I
get the ice-cold isopropyl alcohol from
earlier and I dump it all in very
quickly there's a bunch of this white
stringy stuff floating to the top and
this is the DNA however there are
probably some proteins that precipitate
out as well I try to pull some out with
tweezers but it doesn't really work
I also try scooping it out with a spoon
but that had problems as well
so instead I just mix things up and I
waited for all the DNA to float to the
top after several minutes it was much
more compact and clumped up so it was a
lot easier to scoop out
I transferred it to a coffee filter and
I waited for most of the liquid to drain
through then it was thoroughly washed
several times with cold isopropyl
alcohol afterwards I was left with this
soft and gooey DNA but now I need to
wait for the alcohol to evaporate I put
it on a piece of paper and it took about
a day or so for all the alcohol to
disappear by the time it fully dried it
had turned slightly brown and it was
quite hard I imagined the brown color is
just due to oxidation of some impurities
that were extracted along with the DNA
however I'm not entirely sure just to
show you how hard it is I dropped it on
a watch glass and you can hear the
clinking sound that it makes the mass of
the DNA here is about 250 milligrams and
I got this from 10 strawberries so each
one contains about 25 milligrams because
the DNA is made of lots of long fibers
it's surprisingly strong it was a lot
easier just to use my fingers and tear
it up like a piece of paper but it still
wasn't the easiest thing to do I decided
to try chopping up some of the pieces
again and I was honestly impressed with
just how much force it took anyway now I
think it's time to try eating it
okay so here I have the DNA that I
extracted and it's this very small
amount in the bag
I'm just gonna take out small little
piece now give it a taste
ah it has a there's a really terrible
terrible texture that first is just hard
but after it just kind of gets slimy and
it just tastes kind of salty doesn't
have anything else besides that I think
the salt is either from salt I didn't
wash off after the extraction or it's
actually from the sodium ions that are
associated with the DNA in either case
if the flavor isn't too strong but it's
just vaguely salty slimy and gross
as usual a big thanks goes out to all my
supporters on patreon everyone who
supports me can see my videos at least
24 hours before I post it to YouTube and
they can also directly message me all
supporters with five dollars or more
will get their name at the end of the
video like you see here
[Music]