Hi. This is Mr. Andersen. And I get a lot of e-mails from students around
the country and they want me to give them a shout out. And so I'm going to give them
shout outs now at the bottom of this video. But the student's in my 3rd period AP Biology
class complained a little bit about that, and they wanted to know why I didn't give
a shout outs to them. So what I thought I would do is give them a video shout out. So
if you would, period 3 let's see it. Okay. This is Mr. Andersen. And today I'm going
to be drawing out the central dogma. Since it's hard for me to actually look at the camera
and draw, I'm going to shrink my head and get that out of the way. Now first of all,
what is the central dogma? The central dogma is a term that was coined by Francis Crick.
And so after they discovered the structure of DNA and the DNA if we draw out what it
looks like, DNA looks like this. It's a double helix. And so this would be a helix on one
side. And another helix that kind of wraps around that. And looks like this. So once
they figured out the structure of DNA the next job was to figure out, okay, well how
do we actually take DNA and then make something out of it. And so how do we go from DNA to,
this, let's us red for RNA, to messenger RNA. And then how do we go from messenger RNA eventually
to, let me put you way down here. So how do we actually go to you? So how do we get from
DNA to messenger RNA and eventually to you. So what I'm going to try and sketch out is
how that process actually works. And so let's first of all start on the left side with DNA
to messenger RNA. So first of all what does messenger RNA look like? Messenger RNA looks
like this. If we were to sketch out what it looks like it's linear. So it's just one line.
On one side we have what's called the 5 prime cap. And that's kind of like a head on this
side that identifies this as messenger RNA. On the other side we have what's called a
poly A tail. So that's a bunch of adenines in a row. And so what that cap and the tail
do is they actually protect the messenger RNA. And so how do we go from DNA to RNA?
There is a protein called RNA polymerase. And what it'll do is it'll cruise down one
side of the DNA and it will read off the letters and then put them into messenger RNA. And
so in my sketch here, to keep track of everything, what I'm going to do is I'm going to draw
a line all the way across. And on top of that line, this is going to be inside the nucleus.
And then on the bottom of this is going to be in the cytoplasm. And so the first thing,
anything above this is going to take place in the nucleus. And so let's go back to a
color that is DNA. So DNA, if we get even more specific into what DNA looks like, it's
going to have a backbone that looks kind of like this. It's going to have a side to it.
And so this is going to be what's called the 3 prime end. And then on the other side we
have what's called the 5 prime end. And then they have letters on the inside. And those
letters are what are called nucleotides. And so let's sketch out what those letters might
look like. So this would be one. This would be another letter. And then let me put some
letters that go with this. So this would be the letter A. This stands for adenine. This
would be cytosine. This would be another cytosine. This would be another adenine. This would
be a guanine. And then this on this side would be a thymine. So there are 4 different types
of letters but they're organized in specific ways. And so you'll notice on here that some
of these actually protrude a little more into the middle. Adenine is actually a purine.
So that means it's a double ring structure. So it scoots out a little bit more. And it
will always match with thymine. So you can almost imagine in your head the other side
of the DNA and how the thymine would hydrogen bond perfectly to the adenine and guanine.
And it's going to fit perfectly with the cytosine. And so if we were copying DNA, the DNA simply
splits in the middle and the DNA polymerase is going to add the complimentary side. But
that's not what we're doing. What we're trying to do is show how we can go to RNA from that.
So let me draw the RNA. So RNA is going to look like this. It also has a backbone but
it's just linear. And so opposing the adenine we're going to have a uracil. And opposing
the cytosine we're going to have a guanine. Opposing the other cytosine we're going to
have another guanine. On the other side of the adenine we're going to have a uracil.
On the other side of the guanine we'll have a cytosine. And on the other side of the thymine
we're going to have an adenine. And so the information that was up here is now information
that is in the messenger RNA. And that can eventually leave the nucleus and enter into
the cytoplasm. And so what does that actually look like? Let me choose another color. If
we were to go out here into the cytoplasm, so on the big scale, if something totally
microscopic can be the big scale, we've got our messenger RNA that looks like that. Let
me try and do that in the right color. It's going to have a cap on it. It's going to have
a poly A tail on that side. So this will actually scoot out through the pours in the nucleus.
And the first thing that's going to grab ahold is going to be the bottom of a ribosome. We've
then attach a transfer RNA. And the first thing that will attach to that is always a
thymine. And then we have other transfer RNAs that will just keep coming in. And each of
those are going to bring a different amino acid. And so eventually what you get is a
string of amino acids. And each of those amino acids will eventually become part of a protein.
So the other part I'm missing on here is the ribosome. So this would be the ribosome here.
This would be the messenger RNA. And then these are going to be the transfer RNAs that
pull each of their amino acids to the middle. And so this is how it takes place in the cytoplasm.
If we were to go over here and use kind of our code again, amino acids will say are black.
Amino acids are going to look like this. So this would be one amino acid. These three
letters in messenger RNA are what are called a codon. And those are going to code for a
specific amino acid. In this case UGG, and you'd have to use a chart to figure this out,
is going to code for tryptophan. And the next three letters, UCA are going to code for a
different amino acid. And in this case that's going to code for serine. And so the process
by which we go from DNA to messenger RNA, that process is called transcription. What
we're really doing is we are scripting or we are writing out the message in the DNA
in messenger RNA. This next process is called translation. Translation is when we take the
messenger RNA and actually make a protein out of it. Now is this a protein right here?
No. This is simply a polypeptide. It's a bunch of amino acids attached together. That protein
will eventually fold into a specific shape with alpha helixes and beta pleated sheets.
And it will have a three dimensional shape that gives it a specific structure. And so
if we were to draw out what a human looks like. Let me try to do my best at this. And
let's give this guy some glasses. And maybe we'll give him a chin. and a nose. And a mouth
like that. So when he have a guy like this, who has for example red hair, the color of
that red hair is a protein. And the protein was created by the DNA making messenger RNA
and eventually making a protein. In this case it's for red hair. Or maybe it's for freckles.
Or maybe it's for blue eyes. And each of those is a protein. And that protein's message was
in the messenger RNA. Before that it was in the DNA. And so this whole process is called
the central dogma. It's how we go from a message in the DNA to a message in the messenger RNA.
And eventually we go to you. And so I hope that's helpful.