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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!