Biology Video 5 – Components of DNA
(6)(A) identify components of DNA, and describe how information for specifying the traits of an
organism is carried in the DNA; (6)(B) recognize that the components that make up the genetic code
are common all organisms
‘Sup, everybody! It’s me, Lisa D, again. I was just talkin’ to my girl Haley. We were talking about how
these scientists took the DNA of a fish that lives in, like, the North Pole and put it into a tomato plant.
That way, the tomato could make its own natural antifreeze, the same kind that the fish makes. That
way the tomato plant won’t die in the winter. That’s crazy, right? Do y’all wanna know how that’s
possible?
Well it’s all because DNA has the information for making the traits of all living things. The fish’s DNA
ladder is the same as the tomato’s DNA ladder. Let’s talk about what this stuff is. What does DNA stand
for? DNA stands for deoxyribonucleic acid. Your remember hearing about nucleic acids, right? Yeah, one
of the Big Four biomolecules.
Okay, here’s the DNA ladder. We’ve all seen this before. You might even remember that since DNA is a
nucleic acid, it’s made up of the nucleotide building blocks. One DNA ladder is made of, I don’t know,
trillions of nucleotides! Now don’t lose me here. Remember, all we’re talkin’ about are the building
blocks that make up a DNA twisted ladder that we’ve all seen before. You could also say that DNA’s
shape is a “double helix.” Sounds kinda cool, right? Anyway, let’s take a closer look at these
nucleotides.
So this picture shows us the red-and-yellowy version of a nucleotide. Each nucleotide has three parts.
This tiny, circle-part here? That’s the phosphate. The phosphate group just connects one nucleotide to
the next. To me, that’s all a phosphate group really is, like a connector.
Now see this red pentagon? This red pentagon is a sugar called deoxyribose. To me, it’s the center of
the nucleotide. So you now you have the center and the connecting part of the nucleotide. Some
people call this the phosphate-sugar backbone, but I think we can agree that DNA looks more like a
ladder. So, they’re kind of like the phosphate-sugar sides. Yeah! We should call them the phosphatesugar-ladder-side-thingies! I don’t know. Anyway, let’s take a closer look at the steps of the ladder.
Now, the steps of the ladder are the nitrogen bases. To me, the most important part of the ladder. It’s
the sequence of the nitrogen bases that make up the code, but how? That’s what Haley and I were
talking about.
Well, there are four different bases: A, T, C, and G, which stand for adenine, thymine, cytosine, and
guanine, but that’s not gonna be on the test of life, y’all, thankfully. Let’s look at this ladder again. The
bases on side 1 of the ladder stick to the bases on side 2 of the ladder. You see? It’s like the nitrogen
bases are the steps of the ladder, and the phosphates and sugars are the sides of the ladder. Remember
that.
Now, let’s pump the brakes again, folks. Big picture time. All we’re talking about are the subunits, the
building blocks of the DNA twisted ladder. You might see them like this, or like this, or like this, or even
like this. But remember, it doesn’t really matter how you’re looking at it, because the most important
part are their nitrogen bases, the steps of the ladder.
So like I was saying, the bases stick together, but they stick together in a specific way. Let’s go back to
that black-and-white picture. Do you see what’s happening? The A’s are attracted to the T’s, and the G’s
are bonded with the C’s. Those are the rules for how these bases pair up. Let’s take a closer look at
that.
Alright, take a look A::::T, “AT.” That makes a word, right? C::::G doesn’t make a word. It’s an easy way
to remember; A goes with T, C goes with G. This means that for every T, there’s gonna also be an A. So if
a DNA ladder has, like, 57,000 G’s, there’s also gonna be 57,000 C’s. Cool?
So let’s take a look at this ladder again. What we’re gonna do is fill in the missing parts of the DNA
ladder, and then we’re gonna call it a day. Whatta y’all say, OK? Now, this is not an art class, so no
haters.
So here are the sides of the ladder, side one and side two. Now what are the sides made up of again?
That’s right, the sugars and the phosphates. Great. Now let’s look at the steps of the ladder, the
nitrogen bases. A lot of times, I’ve seen them look like puzzle pieces that fit together. So that’s how
I’ve drawn them. Again, no haters.
So, if I just give you a T up top here and a G here, we can fill in the rest of this DNA ladder. So first things
first, what’s gonna go with this T at the top? Do you remember? Right, an A. So let’s also fill in an A
right here. And now we know that the corresponding blue base down here is also an A. Let’s write that.
Now what’s going to go with this G? Word. C’s. So let’s fill in our C’s. And now we just have two left. Do
you know what goes in the last two? You got it. You’ve got a G here and a T here, and we’re done!
We’ve just filled in a DNA ladder. Amazing!
Alright guys, well that’s what DNA is made of. And what’s cool is that my A’s, T’s, C’s, and G’s are the
same as your A's, T’s, C’s, and G’s! Amazing, right? And that fish and that tomato plant that Haley and I
were talking about? Well the nucleotides of the fish are the same as the nucleotides of the tomato
plant! Trippy, right! DNA is universal! But how does it work? Well, guys, that’s a question for next time.
Until then, this is Lisa D!