Video Transcript: DNA Structure and Function

DNA Structure and Function

Today we're going to talk about DNA. And 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 nutso real world example. If you've ever seen the movie Jurassic Park, you know, it has the storyline where some scientists find a mosquito trapped in amber. Now, the idea is this mosquito had once fed on a dinosaur, so it had dinosaur blood inside it. The idea being that it had a molecule then that was in this blood known as DNA, and they use 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 want it to clone an iguana? I don't know why I picked iguana. Like I just liked the name iguana. Well, if you wanted to clone an iguana, you would need to have a reptile egg. So you would need to take the DNA out of that reptile egg cell. And then you would need to put the DNA of the iguana into that reptile egg. So basically, you took the DNA out, you made it kind of like an empty slate, and you put the organism you wanted to clone the iguana, you put its DNA inside that egg, so that egg cells basically now program to develop into that iguana that organism, it would need to be implanted somewhere so that it can develop. Now, keep in mind that it still would hatch into a baby iguana. But over time, that iguana would develop in there'd be some environmental conditions that might make it look slightly different than the original because the environment can affect how the organism will look, into also how genes function. But the iguana would be a clone an identical copy, because the genetic material that DNA would be the same.

There are a lot of ethical debates with cloning, or really any biology topic that involves DNA. because DNA is the most important molecule with 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 too, that students sometimes don't understand is that all of the cells in your body, every single cell has your entire DNA code each of them. So you know, if you've ever watched those shows CSI or law and order, you know how the criminal can leave behind a hair sample or a skin sample or a blood sample. And they can link that and find the criminal sometimes, if they get a good sample. The idea is even leaving behind a hair that has hair follicles, so 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 all 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'd 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 and your skin does a good thing. Well, in maybe a stomach cell that would be turned on be activated. We call that gene regulation, 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. And if you remember the biomolecules, remember how the biomolecules included carbs, lipids, proteins, and nucleic acids? Nucleic acids are the type of biomolecule that DNA falls under. And like all biomolecules, there are building blocks called monomers. The building block of a nucleic acid is a nucleotide. Okay, so I know that kind of 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. And if you don't understand what DNA is made of, you won't understand how it functions. And if you don't understand how it functions, well, that's going to be really difficult. Really start undersanding how we work. Before I 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 that deoxy ribo. That's for deoxy ribose, 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 called DNA is 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, they really directly code for your traits. There are four bases in DNA. And a lot of times they'll just use the initials A, T, G, and C. The A is for adenine. The T is for 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. And if you don't have them paired correctly, or maybe they get mismatched, that's actually what we call a mutation, which we'll get to a little bit later. But here's the little way you can remember it. Apples on the tree that tells you that go for apples, T for tree, and t always go together. And then the other little verse is cars in the garage, that can help you remember that the base C always goes with the base G, so you kind of know how they match. And DNA pairs this way. DNA has two strands. So there's nucleotides running up one side, and there's nucleotides running up the other side. The bases are what pair in the middle, they're usually held together by hydrogen bonds. The DNA is also twisted, and something we call a double helix shape. And so as that string of strands of the DNA is twisted around, the bases should be all in the center. 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, they contain all of your DNA. Although the DNA is not always turned on completely in all the cells, it depends on what the cell's function is, whether it's going to be turned on or off. That's called gene regulation. We talked about DNA is a type of nucleic acid, and that nucleic acids, which is a biomolecule, are made of nucleotides. And nucleotides contain three parts a sugar, a phosphate and a base. It's the base that codes for your traits. And we talked about which bases match, you can help remember that apples on the tree cars in the garage to give you a little nice way to remember it. Remember, we really have to understand DNA in order to understand how our own bodies function. And 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