字幕表 動画を再生する 英語字幕をプリント Hi. It's Mr. Andersen and I'm going to preview the genetics unit. This is unit 5. If you want to check out this prezi that I'm going through, you go to bit.ly/geneprezi. And it's going to show you basically this concept map and then it's going to have links to all of the videos within this unit. And so the big picture within this basically I'm going to talk about two major things. Number one is genes. How they're made of DNA and how they get copied from cell to cell. And then more of the details of genetics. And so we start by looking at what a gene is. And how a gene is defined. And so a gene remember is going to be made of DNA. So the first thing that we'll cover within this unit is what is DNA? What is the structure of DNA? We begin with part one with the talk of the history of DNA. How DNA is put together. But more importantly in this unit we're going to talk about how DNA becomes RNA. And how RNA eventually becomes proteins. And so we call this whole thing the central dogma. And so in the first part I talk about DNA. In the second part I'm going to talk about transcription, translation and how DNA is replicated. And this video right here where I talk about the central dogma, I'm going to talk about that, really the meaning of life. How cells take information in the DNA. They make a transcript of that. Make messenger RNA and eventually make proteins out of that. And I'm going to draw all of the parts of that. So these three videos summarize that central dogma of life. After we're done with that we're going to move to the cell cycle. And so the cell cycle is how we make sure that DNA gets passed from cell to cell. And also from generation to generation. And so the two terms that you're maybe familiar with are going to be mitosis and then meiosis. If we were to talk about the two, mitosis is basically taking one cell, let's put a nucleus here and it's got DNA on the inside. And how we divide that to make two cells and each of those cells are going to be daughter cells, but they're going to be identical to that first cell. And so in mitosis we're taking one cell and making two copies of it. That's how we go from that first cell inside you, that zygote, to the trillions of cells inside your body. Inside that first cell we are diploid. So we have two complete sets of chromosomes. And each of these cells remember are going to be diploid as well. In meiosis, whenever you see the word meiosis, you should think about the word sex. Because meiosis is how we make sex cells or how we make gametes. And so that's starting with one cell, we'll make that two n. So it's got a nuclei like this. And it's basically going to divide in half. And then those cells are going to divide in half. And so we're going to end up with 1, 2, 3, 4 cells. Instead of each of these being identical to that first cell, each of these are going to have half the genetic information. And they're also going to be totally different than that first cell. And so in males each of these will become a sperm. And in a female one of these, let's choose this one down here, one of these is going to be the chosen egg and the other nuclear materials is going to wad up and not become anything. And so that's meiosis. And so basically mitosis is how we copy all of the DNA and make sure that it ends up in each of the different cells. A better way to define what mitosis is is simply nuclear division. It's going to be part of the cell cycle. But meiosis is how we create different nuclei in each of those. Remember, sex cells. And so that's the cell cycle. And then the next thing we're going to cover in the genetics unit is going to be genetics. And genetics is two fold. Genetics is going to be Mendelian genetics. And so in Mendelian genetics we're going to to do genetics of Mendel. And so this is Gregor Mendel right here. Gregor Mendel, you've probably heard of this, was a monk. Studied genetics. Studied pea plant characters and traits. He actually dies in obscurity. Nobody really pays attention to him. But you've learned a lot about Mendelian genetics hopefully throughout your science career. It's how we take lets say these are purple flowers and these are white flowers. And if we take purple flowers that are hybrid. Cross those with purple flowers and so you've done those punnett squares before. So this would be big P little p big P little p. So if you've done those and figured out this is going to be a three to one ratio. So that's going to be all the work of Mendel. So he figured out that we've got basically the idea that we've got genes. They're passed from generation to generation. You've got two genes. And you're going to give one of those randomly to your offspring. The idea of independent assortment. So that's the Mendelian genetics or basic genetics. And then we're going to deal with advanced genetics. And so advanced genetics doesn't mean it's any more complicated. It's going to summarize the work of this guy. This is Thomas Hunt Morgan and his work with fruit flies. But basically what we figured out with advanced genetics is that Mendel's laws don't always work. Lots of times the genes are on the same chromosome and so you've got gene linkage. We also figure out that in some genders there are going to be some genes that are found on the sex chromosomes. And we also add to this multigenic inheritance. And so traits for example, like height that are caused by a number of different genes. Incomplete codominance. So we're going to add a lot of things to that. And so that's genetics. Non Mendelian genetics. And then that last thing that we're going to talk about in this unit on genetics is gene regulation. And so basically if you look at a cell. So if this is a cell on the inside it's going to have DNA. But not all of the DNA is going to be expressed. In other words not all of the DNA is going to make messenger RNA. And then make proteins. So, that's kind of bad writing, but in this unit on gene regulation we're going to talk about how we can turn genes on and how we can turn genes off. And that begins with a discussion of the operon which is found in bacteria. And it's a simple way that they turn genes on or genes off. And then in eukaryotic cells we're going to talk about transcription factors and how they can turn a series of genes on or genes off. And so that's how we'll finish out the unit on genetics. And so that's a preview of the unit to come and I hope that's helpful.