- [Voiceover] So in this video,
we're going to be talking
about something known
as DNA hybridization.
DNA hybridization.
Alright, so in this video
we're going to be talking
about something known
as DNA hybridization.
So, DNA hybridization.
Now, what is DNA hybridization?
Well, basically what it...
So, let's work through an example to try
and explain what DNA hybridization is.
So, let's imagine that we have two cells.
So over here we have Cell A
and over here we have Cell B.
Now, let's imagine that
Cell A is a cancer cell.
So, this is a cancer cell.
And Cell B over here is a normal cell.
So, this is normal.
Now, cancer cells
basically have the ability
to proliferate and grow and grow
and metastasize and move
throughout the body.
So, basically they have this
unregulated cell growth.
And the reason that the
cell growth is unregulated
is because there are various mutations
that cause changes in the proteins
that are expressed
and changes in the
regulation of the cell cycle.
And there are hundreds and hundreds
of different mutations
and hundreds of different proteins
that could be effected.
And, all of them can lead to cancer.
Now, one is producing different proteins
in different amounts.
Now, what are kind of the two options
that we have for certain genes?
So, let's imagine that
we have Gene A over here.
So if this is Gene A,
what are the two options?
Either Gene A can be upregulated
or it can be downregulated.
So if it's upregulated then what we have,
is we have the gene products,
which is mRNA and eventually protein,
we have a lot more of
the mRNA and the protein
that Gene A encodes for.
And what that basically means is that,
let's imagine that Gene
A encodes for a protein
that will induce cellular proliferation
and will allow that cell
to go and metastasize
throughout the body.
Well, if we have a lot more
of Gene A being expressed,
either because the promoter is upregulated
or for whatever reason,
now we have lots and lots of this protein
that basically allows
cellular proliferation
to occur.
We have lots of this protein floating
around the cell and we
have this cancer cell
proliferating uncontrollably.
So, another option is if we have Gene B,
so if we have Gene B.
Gene B could be downregulated.
And that basically means that Gene B
isn't producing its gene product.
And what if that gene
product were something
that basically stopped this
cell from proliferating.
Well, if we have less inhibition
then we basically have more proliferation.
And the third option for any specific gene
in a cancer cell,
so let's say Gene C,
is that there's no change.
So, there's just no change.
So, we what we want to do is use
DNA hybridization technology in order to
assay the gene transcription profiles
of a cancer cell compared
to a normal cell.
And in order to do that, we need to use
something known as a microarray.
So, a microarray.
Now, what is a microarray?
Well, array basically means that
we're assaying a whole
bunch of different things.
And in this case, we're assaying
the transcription profiles of a bunch
of different genes.
And micro just means that it's small.
So, this could be as small as a chip.
So, let's imagine that we
have a microarray chip.
So, let's say that we've got this chip
and it's basically just this square.
And this chip has a lot
of different holes in it.
So let's imagine that we've
got lots and lots of holes.
So we have just hundreds of these holes.
And I'll just draw a few
for simplicity's sake.
So we have a bunch of these holes
on the mircoarray chip.
Now these holes are
actually little tiny wells,
they're microscopic wells.
So if we actually looked
at this from the side,
so here's the chip, we're looking at it
from the top.
It's lying on the table,
we're looking down at it.
If we looked at it from the side,
one of these wells would look like this.
And inside the well would be the,
would be a complimentary mRNA strand.
So, we've got just lots and lots of these
little complimentary mRNA strands.
And what are they complimentary to?
Well, they're complimentary
to a specific gene.
So, let's say that inside
one of these wells,
let's draw another well over here.
Let's say that inside one of these wells,
we have the complimentary mRNA to Gene A.
So we've got the
complimentary mRNA to Gene A.
Now let's imagine that
in this cancer cell,
Gene A is upregulated for whatever reason.
And if Gene A is upregulated,
it's being overtranscribed and that means
that there's lots and
lots of the Gene A mRNA
floating around in this cell.
So there's just a bunch
of the Gene A mRNA.
And this is in comparison
to the normal amount
of Gene A products,
which might just be a few Gene A mRNAs.
Now, what we can do, is
we can take this cell
and we can break it apart.
And we can label the mRNA
with a certain color.
So let's say that I label
each one of these mRNAs
with a yellow fluorescent label.
So, let's imagine that I
labeled every single one
of the mRNAs with a
yellow fluorescent label.
And let's imagine that I labeled the mRNA
in the normal cell with
a blue fluorescent label.
Now what I can do is I can
break these cells apart
and I can basically add
the intracellular contents to this well.
So, I can add it to this well.
And since I have lots
and lots of this mRNA
that's labeled yellow,
what I'm going to have,
I'm going to have a lot of the mRNAs
binding to the complementary strands.
And so I'm going to have a
really bright yellow well.
And when I add the normal
cell intracellular contents,
I'm going to have some blue.
So, I'm going to have lots of yellow
and a little bit of blue.
And what that'll basically look like is,
it'll really just, you won't
be able to see the blue,
it'll really look like
just a bright yellow dot.
So, let's imagine that this is the well.
It'll look like a bright yellow dot.
And a computer can scan every
single one of these wells
and basically decide, "okay,
is it a brighter yellow
or is it a brighter blue?"
If it's a brighter yellow color,
if you see mainly yellow,
that means that you have a lot more
of that specific gene's products
being expressed in the cancer cell
compared to the normal cell.
Now, let's imagine that we
look at a downregulated gene.
So it we look at a downregulated gene,
let's just draw another well.
So let's draw a well over here.
Now, if we look at a downregulated gene,
we've got lots of the Gene B mRNA,
the complementary
strands, inside this well.
And we're going to have very few
of the Gene B mRNA in the cancer cell
and then a lot more in the normal cell.
And once again, we'll
label the Gene B mRNA
with a yellow fluorescent label.
And over here, again, I'm sorry,
over there, we're going to label it blue.
So, we'll label it with
this blue fluorescent label.
And once again, we're
going to lice the cells
and expose the intracellular
contents to this well.
And what we're going to have,
we're going to have very few
of the Gene B products binding
and we're going to have
a lot of the normal cell,
of the Gene B byproducts in
the normal cell, binding.
So, when you look at this well,
it's going to pop up as mainly blue.
And once again the
computer's going to read this
and it's going to notice,
"oh, well, this well has mainly
a blue fluorescent label"
which means that the normal cell is
expressing a normal amount
and there's a lot less of that gene
being expressed in the cancer cell.
So, this is kind of the
idea of a microarray chip
and assaying the gene expression profile
in a cancer cell versus a normal cell.
It's able to tell you
whether a specific gene
is upregulated or downregulated.
And you're also able to see if
a specific gene has no change
and if there's no change,
then instead of seeing either
a yellow or a blue dot,
you would see something
kind of in the middle.
So, maybe you'd see a green dot.
And that's basically a quick way
in order to look at a whole bunch
of different genes on a single chip
and try and quickly
determine which gene is
upregulated or downregulated
in a cancer cell compared
to a normal cell.
And this can help you
tailor your therapies.
So, let's say that you know that this well
right here is for a specific protein
and you have a drug that's
able to target that protein.
Well, now, you're able
to tailor your therapy
for that individual patient using
this microarray technology.
