Captioning is on! To turn off, click the CC button at bottom right. Follow the amoebas on Twitter @amoebasisters or on Facebook! Today we’re going to talk about DNA. We’re
going to go into the structure and the function of DNA, but before we do that, we want to
talk about why DNA is so awesome. So let me give you a not so real world example. If you’ve
ever seen the movie Jurassic Park, you know it has a storyline where some scientists find
a mosquito trapped in amber. Now the idea is that this mosquito once fed on a dinosaur
so it had dinosaur blood inside it. The idea then was that it had a molecule inside it
known as DNA. The scientists used the DNA to clone and create dinosaurs. Now there are
some unrealistic things in this, but the idea of cloning is not unrealistic because actually
it can and does occur. Say for example you wanted to clone an iguana. I don’t know why
I picked iguana…I think I just like the name iguana. Well if you wanted to close an
iguana, you would need to have a reptile egg cell. You would need to take the DNA out of
the reptile egg cell. Then, you would need to put the DNA of the iguana into that reptile
egg cell. So basically you took the DNA out of the egg cell and made it like an empty
slate, and then you put the organism you wanted to close- the iguana- DNA into that egg cell.
That egg cell is now basically programmed to develop into that iguana. It would need
to be implanted somewhere so that it could develop. Now keep in mind that it would still
hatch into a baby iguana. But over time, that iguana would develop and there would be some
environmental conditions that would make it look slightly different from the original.
The environment can affect how the organism will look as well as how genes function. But
the iguana would be a clone, an identical copy, because the genetic material (the DNA)
would be the same. There are a lot of ethical debates in cloning or really any biology topics
that involve DNA, because DNA is really an important molecule for life. It controls all
of your traits. Your cells can’t function without it. How tall you are, what color your
eyes are, what color your hair is, or even if you’re at risk for certain diseases like
heart disease or cancer…some of that can be found in the DNA. Your DNA is just incredibly
important. One thing to that students sometimes do not understand is that all the cells in
your body has your entire DNA code. Each of them. So if you ever watch those shows like
CSI or Law and Order—you know how the criminal can leave behind a hair sample or skin sample
or blood sample? They can link that to the criminal sometimes if they get a good sample.
The idea is that even leaving behind a hair that has hair follicle cells, you can get
the entire DNA code. Because every cell has all of your DNA. One thing to point out: even
though all of your cells contain your entire DNA code, that DNA is not “turned on”
all the time in all of your cells. Let me give you an example. A skin cell is NOT producing
digestive enzymes – that would be nasty. The digestive enzyme, even though it’s coded
for in the DNA and your skin cells like all cells have all of your DNA, that is turned
off in your skin, which is a good thing. While in maybe a stomach cell that would be turned
on and activated. We call that gene regulation; it’s the ability to turn genes on and off.
So let’s talk about the structure of DNA. First of all, DNA is a type of nucleic acid.
If you remember with the biomolecules, they included carbs, lipids, proteins and nucleic
acids. Nucleic acids are the type of biomolecules that DNA falls under, and like all biomolecules,
there are building blocks called monomers. The building block of the nucleic acid is
a nucleotide. I know I’m bombarding you with vocabulary, but it’s really important
to understand the parts of a nucleotide because otherwise you don’t know what DNA is made
of. If you don’t know what DNA is made of, you won’t understand how it functions. If
you don’t understand how it functions, well, it’s going to be difficult when we start
understanding how we work. Before we get into the three parts of a nucleotide, I do want
to point out the name of DNA. So DNA stands for deoxyribonucleic acid. That’s what the
NA part is – nucleic acid. And that “D” is for deoxyribose which is a sugar. So nucleotides
have three parts, and one of them is a sugar called deoxyribose. The next thing is a phosphate.
The phosphate is involved with the sugar in helping hold the DNA structure together. We
sometimes call DNA as having a sugar-phosphate backbone. But the most important part of the
nucleotide is the base, because the bases actually code for traits. So as far as the
bases go, again those are the important parts that control your traits, there are four bases
in DNA. A lot of times they’ll just use the initials: A, T, G, C. The a is for adenine.
The T is thymine. The G is for guanine, and the C is for cytosine. There’s a really
nice little saying that can help you remember which one goes with which because these bases
actually pair in a correct pattern. If you don’t have them paired correctly, or maybe
they get mismatched, that’s actually what we call a mutation. Here is the way you can
remember it: apples in the tree; that tells you that A for apples, T for trees, because
A and T always go together. The other verse is: cars in the garage; that can help you
remember that the base C always goes with the base G. DNA pairs this way. DNA has two
strands so there are nucleotides running up one side and there’s nucleotides running
up the other side. The bases are what pair in the middle. They are usually help together
by hydrogen bonds. The DNA is also twisted in something we call a double-helix shape.
So, as that strand of the DNA is twisted around, the bases should be all in the center and
the sugar and phosphate make up the sides. So let’s review what we talked about today.
We talked about the importance of DNA that it’s found in the nucleus of cells. That
ALL of your cells, every one of them, contain your entire DNA. Although, the DNA isn’t
always turned on completely in all the cells. It depends on what the cells function is whether
it’s going to be turned on or off. That’s called gene regulation. We talked about DNA
as a type of nucleic acid and that nucleic acids, which is a biomolecule are made of
nucleotides. Nucleotides contain three parts: sugar, a phosphate, and a base. It’s the
base that codes for your traits. We talked about which bases match; remember: apples
in the tree, cars in the garage. Remember, we really have to understand DNA in order
to understand how our bodies function. When we get into genetics, we’ll talk about how
that DNA actually works and how it really codes for traits. That’s it for the Amoeba
Sisters, and we remind you to stay curious!