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Biology: Molecular Genetics: Protein vs. DNA?


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About this Lesson

  • Type: Video Tutorial
  • Length: 9:23
  • Media: Video/mp4
  • Use: Watch Online & Download
  • Access Period: Unrestricted
  • Download: MP4 (iPod compatible)
  • Size: 101 MB
  • Posted: 07/01/2009

This lesson is part of the following series:

Biology Course (390 lessons, $198.00)
Biology: Genetics: DNA & Replication (35 lessons, $54.45)
Biology: Discovering DNA (5 lessons, $13.86)

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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Recent Reviews

good beginning
~ Laurie8

A good teacher

good beginning
~ Laurie8

A good teacher

We're about to really find out the true secret to life on this planet. When we start talking about the way cells work, the whole drive behind what is the central dogma, you and I both have to think about something. What would make something the "brain" of the cell? What would you give the genetic material, what qualities? Well if I was thinking about it, gee, this is a pretty big responsibility. What am I going to give to the material that is going to run my cell? Well number one, it has to be informational. In other words, it has to carry some form of information. Now what that information is, we'll see. Number two- if it's the gene, if it is the stuff that runs my cell, it has to be capable of replication. In other words, it has to be able to pass that information on, because we know that cells replicate. And therefore, the information carrying machinery has to replicate also. Number three- it has to be capable of "talking." It has to be able to communicate within the cell, and run the machinery of the cell, whatever that machinery is. And number four, through the course of evolution, we know that things have changed. It has to have some kind of capacity for change.
So as you and I start to think about what is this genetic material, and how does it work, these are the four things I want you to keep in mind. It has to be informational, capable of replication. It has to be able to talk to the cell. And it has to have a capacity for change. And you know what, that was the debate that was entered over 100 years ago. And that's what I want to talk to you about now.
Sometimes you can't really understand where you are unless you've seen where you've been. And we're going to take, together, a journey in the past to see how the story of the genetic material was unraveled. And the whole idea of heredity was discovered long before DNA was. As soon as people realized that there was something called a gene, a factor... A guy by the name of Gregor Mendel discovered this. Mendel didn't know it, but he started the journey into what and how genes work. That being said, you have to understand something. Nobody knew what they were. Nobody knew what the genetic material was. In fact, let's think about those whole four priorities, informational, replication, it's got to be able to talk to the cell, capacity for change. We're talking about a very, very complicated material here, complicated sounding.
So if you were one of these guys, in fact, from what you know about biology, think about it. One of the biggest molecules known is a molecule called protein. Think of what you know about protein. Proteins are big. Proteins have all of these different shapes. Proteins do all of these different jobs. You know if I were a guy back in the early 1900s, I'd be saying protein is the genetic material. And you want to know something? A lot of people felt that way. There was a huge debate as to what is the genetic material. And everybody, initially, was going after protein.
Now let's talk about the history. And by the way, I think you know that the answer is not protein. You know we're talking about DNA here, deoxyribonucleic acid. So if you could go back in time, you could probably win some bribes. Tell people, "You're wasting your time. Go after DNA." But let me tell you what these guys did. Let's talk about what DNA is and how it was discovered, and some of the events that happened to get us to this whole idea of DNA is the genetic material.
In 1869, Miescher discovered the stuff in the nucleus of pus. Pus is white blood cells. You may know that. What he did was, he was chemically digesting white blood cells. And what he found was this kind of strange material in the cell, this acidic material in the cells nucleus. It contained phosphorous, and thus was born this new material, this nucleic acid. People went on to investigate it chemically. Realized what it was made out of, what its sub-units were. It turned out to be this kind of simple stuff. It turned out that DNA was this stuff that had four units. And the units were nucleotides A, G, C and T, adenine, guanine, cytosine, thiamin. You know, kind of cool stuff. It was in the nucleus, so that was intriguing. Probably held the true nuclear material together, the true genetic material together, the proteins. But it was nice to know about this stuff. So 1869, little did Miescher know that he was the first step.
1914, some interesting things started happening. A guy by the name of Feulgen developed this staining technique. And what he did was he developed this staining technique for DNA, this deoxyribonucleic acid. And here was the interesting thing about this. Boy now some people started to listen just a little bit. Here's what he saw. What Feulgen did was he came up with a staining technique for DNA. And the more DNA, the darker, so it was a quantitative, grossly quantitative, but a quantitative way to measure DNA. And Feulgen basically found out, using this technique, that all cells of the body, all cells in all organisms, all the cells in any given organism have the same amount of DNA, except gametes, except sex cells.
Sex cells seemed to have approximately one half the amount of DNA as all of the somatic, the body cells. Wow, could this be related to the fact that sex cells are only supposed to send half of their genetic material? And if that's true, could DNA be that genetic material. Nah, I'm sure it was just because there was half the amount of proteins in there, and you needed half the amount of DNA to hold them together. Right? But you never know.
So now we have this whole idea that maybe DNA is more important than we think, but it's protein, big time. 1908, here's a guy ahead of his time, A.E. Garrod. He was a doctor. And he wrote a book. And he wrote a book called Inborn Errors of Metabolism. Now you're going to say, "So what?" But this is 1908, and here's what Garrod wrote. He particularly studied a disease called Alkaptanuria. Here's the thing, a person with Alkaptanuria, it's sometimes called maple syrup urine disease, what happens is their urine turns black. It oxidizes. Not a good thing to have. And they often detected it when babies' diapers turned black. But what Garrod saw was, number one, this was passed on. It seemed to be an inborn mistake, something that was passed on. In other words, some brothers and sisters kind of had the same trait in their family, very, very interesting. In addition, this was an enzymatic disorder. This was an enzyme problem. And now we come to our first link.
The hereditary material had something to do with enzymes. Did that solve the problem? Well of course not, because enzymes are protein. So the protein people were rejoicing. All right, notice the way I said it, something to do with enzymes. There's a lot more to this story coming up.
Molecular Genetics
Discovering DNA
Molecular Genetics: The Protein vs. DNA Debate Page [1 of 2]

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