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Biology: Nucleic Acids - Intro to Genetic Material


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About this Lesson

  • Type: Video Tutorial
  • Length: 10:49
  • Media: Video/mp4
  • Use: Watch Online & Download
  • Access Period: Unrestricted
  • Download: MP4 (iPod compatible)
  • Size: 116 MB
  • Posted: 07/01/2009

This lesson is part of the following series:

Biology Course (390 lessons, $198.00)
Biology: Final Exam Test Prep and Review (42 lessons, $59.40)
Biology: Inorganic and Organic Chemistry (34 lessons, $51.48)
Biology: Lipids and Nucleic Acids (4 lessons, $6.93)

Taught by Professor George Wolfe, this lesson was selected from a broader, comprehensive course, Biology. This course and others are available from Thinkwell, Inc. The full course can be found at The full course covers evolution, ecology, inorganic and organic chemistry, cell biology, respiration, molecular genetics, photosynthesis, biotechnology, cell reproduction, Mendelian genetics and mutation, population genetics and mutation, animal systems and homeostasis, evolution of life on earth, and plant systems and homeostasis.

George Wolfe brings 30+ years of teaching and curriculum writing experience to Thinkwell Biology. His teaching career started in Zaire, Africa where he taught Biology, Chemistry, Political Economics, and Physical Education in the Peace Corps. Since then, he's taught in the Western NY region, spending the last 20 years in the Rochester City School District where he is the Director of the Loudoun Academy of Science. Besides his teaching career, Mr. Wolfe has also been an Emmy-winning television host, fielding live questions for the PBS/WXXI production of Homework Hotline as well as writing and performing in "Football Physics" segments for the Buffalo Bills and the Discover Channel. His contributions to education have been extensive, serving on multiple advisory boards including the Cornell Institute of Physics Teachers, the Cornell Institute of Biology Teachers and the Harvard-Smithsonian Center for Astrophysics SportSmarts curriculum project. He has authored several publications including "The Nasonia Project", a lab series built around the genetics and behaviors of a parasitic wasp. He has received numerous awards throughout his teaching career including the NSTA Presidential Excellence Award, The National Association of Biology Teachers Outstanding Biology Teacher Award for New York State, The Shell Award for Outstanding Science Educator, and was recently inducted in the National Teaching Hall of Fame.

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I hope you guys don't have the impression that things like carbohydrates are the true secret to life or things like lipids are the true secret to life. They're important to life and certainly, without a good lipid now and then ice cream would be very boring. But, you know, if you really want to see what the true secret to life is, we've got talk about nucleic acids. Not that there are creatures without carbohydrates and lipids, I like carbohydrates and lipids. But there is nothing that has determined the function of life and that determines the function of life as much as nucleic acids. Nucleic acids are what it's all about.
How can that be? Well, how important are nucleic acids? Well, we call our knowledge of the way nucleic acids work--they are so important, that we call it the "Central Dogma." Now, how big is that? You don't get to hear about Central Dogma much in science, but this is the Central Dogma. We're talking big stuff here. What is the Central Dogma of biology? It's very simple. DNA makes RNA. RNA leaves the nucleus and makes proteins. We're talking big time Central Dogma here. So, what does this have to do with nucleic acids? Did you ever wonder what DNA stands for? RNA stands for? Well, if you wondered that, you're about to find out.
DNA stands for deoxyribonucleic acid. Nucleus acid. So, it's an acid in the nucleus. What kind of acid? A nucleic acid, which is why we're talking about nucleic acids. This deoxyribose stuff must have something to do with its molecular structure. Now, RNA isn't much different. RNA, which we'll see next, is going to be called ribonucleic acid. A nucleic acid that has something to do with ribose. Well, what I want to do, is I want to talk to you about the basic building blocks of nucleic acids. Both DNA and RNA have one basic building block that is called a nucleotide. Now a nucleotide is found--there are nucleotides found in both DNA and RNA. Let's take a look at a generic nucleotide. Just a plain old, generic, nucleotide.
Now a generic nucleotide, well, I'll draw you one first. Here's the way I like to visualize the generic nucleotide. I like to think of suburbia. Why do I like to think of suburbia? Because here's my picture of suburbia. Suburbia has houses in it. Nice little five corner houses. In suburbia, every house has a driveway. This is why I'm not so sure I should do this, because I live in suburbia and I don't have one of these, but a lot of my neighbors do. They have a pool attached to their house. Now, it doesn't grow out the roof of the house. So, perhaps, that's where the analogy breaks down, but maybe you're looking down on this house.
So, suburbia, house, driveway, pool. Well, this is a nucleotide. Now, obviously, I know you know enough chemistry by now to know these are not called house, driveways and pools. This is a pentose. Let's analyze that word. A pentose is a five-carbon sugar. Ose, you remember ose's. Carbohydrates, ose. Pent, as in pentagon, five. So, this is a pentose. It can be one of two pentoses, we'll talk about that later. This is a base that contains nitrogen or a nitrogenous base. Nitrogen ous base. This is one of those functional side groups that I know you know are so important. This is the phosphate group. So, a nucleotide, a generic nucleotide looks something like this.
Now let's take a look at what this really looks like in terms of its chemistry. Perhaps a slightly better rendition of a nucleotide. Now, we said that DNA and RNA are polymers of nucleotides. Well, let's take a look at what that means. Well, if you take a look at a--let's just do a generic polymer here. I'm not going to say whether this is RNA or DNA. We can see that nucleotides bond together in long chains and this pink area is enlarged right here. So, you see that the polymers are going to be hooked together, and boy are we going to cover that in a lot more detail in later lessons. But, there it is. Phosphate, pentose, nitrogenous base.
Now, let's get into some nitty gritty. What's the difference between DNA and RNA? Let's start out with DNA. DNA, as I said, is deoxyribonucleic acid. Well, you see that whole idea of deoxyribose. Now, ribose--those of you know your carbohydrates really well, probably know that ribose stands for ribose. Ribose is a five-carbon sugar. There's that pentose coming up. Deoxy must mean that it's missing an oxygen. Well, let's take a look at some ribose and compare it to deoxyribos. Five carbon sugar, remember, we number our carbons, one, two, three, four, five. If you take a look at the number two carbon on ribos, you see that it has an oxygen on its O-H group, right there.
On the other hand, if you look at deoxyribos, we see that it's missing an oxygen in its number two carbon. So, one thing about DNA, its sugar, its pentose is deoxyribos. So, we call these deoxyribo nucleotides. Nucleotides that have deoxyribose in them. Deoxyribonucleotides. Let's talk about deoxyribonucleotides. Deoxyribonucleotides, as I said, they lack oxygen in their ribose, but there's more to them than that. Deoxyribonucleotides are going to have that nitrogenous base. That nitrogenous base can be one of four. So, this is kind of cool. Think about it. Phosphate is phosphate is phosphate is phosphate. Deoxyribose is deoxyribose is deoxyribose is deoxyribose. But this is going to be different from nucleotides and there are four of them. We're going to call them A, or G, or C, or T in DNA.
Well, I know you're saying to yourself, "Well be honest with me, what does the A, G, C, or T stand for?" Glad you asked. Let's start with A and G. A and G stand for adenine and guanine. Adenine and guanine are two nitrogenous bases. There's the nitrogen, nitrogen, nitrogen--it's everywhere, nitrogen. That's why they're called nitrogenous bases. They're purines and I want to give you a little clue, a way to remember this, because I'm about to show you something else. You can remember that guanine or adenine are purines by the following trick. PUGA2. What's up with PUGA2? Purines are guanine and adenine and they have two rings each.
Well, there must be something that doesn't have two rings. Right? Yes, that would be a group of molecules called the pyrimidines. Pyrimidines only have one ring. That would be C and T. So, cytosine and thymine are the pyrimidines. How do you remember pyrimidines? Like this, PUGA2, because the purines of quanine and adenine and they have two rings. I don't have one for pyrimidines, but if you remember the purines, you'll be fine.
So, what is DNA? DNA is a polymer of deoxyribose nucleotides, a polymer of deoxyribonucleotides. Well, what about RNA? RNA is a polymer of ribonucleotides. Well, I've already taught you what ribose is all about. Is that the only way it's different? No, there's some structural differences we'll see later, but there's one thing I want to tell you. One more thing I want to tell you about the physical nature of RNA. That has to do with these guys right here, the pyrimidines. In RNA structure we have the same thing, except now we have ribose and we have this nitrogenous base. That nitrogenous base can be A, or G, or C, or U. Not T. There is no thymine in RNA. So, therefore, we now have a third nucleotide, a third nitrogenous base. Nitrogens--it's one ring. So, is it a purine or a pyrimidine. One ring. PUGA2. PUGA2, it's a pyrimidine.
So, we do not have thymine in RNA. We have guanine and adenine and cytosine and uracil. So, one quick summary and then we're out of here. DNA versus RNA. DNA is a polymer of deoxyribonucleotides, so it has deoxyribose. RNA has ribose. DNA has A, G, C, or T. RNA, A, G, C, U. I'm smiling to myself because, you know what, I could go on and on and on with this list because I know a lot more differences than that, but this is just the basics of nucleic acids, and you're just going to have to wait `til later for the rest of it.
Inorganic and Organic Chemistry
Lipids and Nucleic Acids
Nucleic Acids: An Introduction to Genetic Material Page [1 of 2]

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