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Description
This unit is concerned with the cell nucleus. The different stages of mitosis are pointed out and explained by Stephen Hurry. Michael Pentz briefly takes up the topic of nucleic acid as a short int
...roduction to B.S. Cox's experiment in DNA transformation. Cox explains the controls needed to perform the experiment and shows what happened to the controls during the experiment.
| 1 | 00:00:00,000 | 00:00:03,000 | Stephen Hurry: Here’s the nucleus with this nuclear membrane around it. |
| 1 | 00:00:01,000 | 00:00:05,000 | Stephen Hurry: Now let’s review the whole thing again as a continuous process. |
| 1 | 00:00:02,000 | 00:00:06,000 | Brian Cox: This experiment is done with bacteria and it is the… |
| 2 | 00:00:05,000 | 00:00:10,000 | The only structure that can be seen are these dark objects here. |
| 2 | 00:00:07,000 | 00:00:12,000 | ..first and classic experiment demonstrating that DNA is a carrier of genetic information. |
| 2 | 00:00:07,000 | 00:00:10,000 | We’ll see the film through, and remember that this film is… |
| 1 | 00:00:08,000 | 00:00:12,000 | Michael Pentz: This is what Unit 17 is all about. |
| 3 | 00:00:11,000 | 00:00:14,000 | ..speeded up a great deal so that condensed into a few moments… |
| 3 | 00:00:12,000 | 00:00:16,000 | These are called nucleoli. They have no function in cell division. |
| 2 | 00:00:13,000 | 00:00:18,000 | The nucleus of the cell, the stuff inside it, |
| 3 | 00:00:14,000 | 00:00:20,000 | Here are two cultures of bacteria. They are identical, except in one respect. |
| 4 | 00:00:14,000 | 00:00:16,000 | ..is a process which will last a whole day. |
| 4 | 00:00:17,000 | 00:00:22,000 | Notice that the rest of the nucleus contains apparently nothing special, |
| 3 | 00:00:19,000 | 00:00:23,000 | what it is, what it does, how it’s organised. |
| 5 | 00:00:19,000 | 00:00:24,000 | Here’s the Interphase cell with little structure visible. |
| 5 | 00:00:23,000 | 00:00:27,000 | but chemical activity is going on here and it’s at this stage… |
| 4 | 00:00:24,000 | 00:00:29,000 | The cells in this culture are lacking an enzyme… |
| 4 | 00:00:24,000 | 00:00:28,000 | Our programme is going to be in two parts and in the first part Stephen Hurry… |
| 6 | 00:00:26,000 | 00:00:30,000 | And we’ll jump, yes, into Prophase. |
| 6 | 00:00:28,000 | 00:00:33,000 | ..in the division process, that the DNA is duplicated. |
| 5 | 00:00:28,000 | 00:00:34,000 | ..will be going through the division, the role of the nucleus in cell division. |
| 5 | 00:00:30,000 | 00:00:33,000 | ..which is required to make a simple amino acid Tryptophan. |
| 7 | 00:00:32,000 | 00:00:41,000 | Chromosomes are distinct, and now they’re free in the cell substance. |
| 6 | 00:00:34,000 | 00:00:38,000 | The cells in this culture possess that enzyme and so they can make Tryptophan. |
| 7 | 00:00:34,000 | 00:00:36,000 | This stage is called Interphase. |
| 6 | 00:00:34,000 | 00:00:37,000 | He’ll be showing you a greatly speeded up film for that. |
| 8 | 00:00:38,000 | 00:00:44,000 | What happens next? Well, inside the nucleus the chromosomes become apparent. |
| 7 | 00:00:38,000 | 00:00:41,000 | And in the second part, we’ll be probing a little more deeply… |
| 7 | 00:00:40,000 | 00:00:43,000 | Now I’m going to show you how we can tell the difference, quite simply, |
| 8 | 00:00:42,000 | 00:00:45,000 | ..into the function of this stuff. |
| 8 | 00:00:44,000 | 00:00:48,000 | between these two cultures. Here are two plates. |
| 8 | 00:00:44,000 | 00:00:47,000 | Remember that they’re duplicated already. |
| 9 | 00:00:45,000 | 00:00:49,000 | The nucleoli vanish and the nuclear membrane bursts apart. |
| 9 | 00:00:46,000 | 00:00:49,000 | Stephen Hurry: For your home experiment you’ll be working… |
| 9 | 00:00:49,000 | 00:00:52,000 | They contain a simple growth medium. |
| 10 | 00:00:49,000 | 00:00:51,000 | ..with a still photograph of a number of cells in division. |
| 10 | 00:00:50,000 | 00:00:54,000 | Watch it here. We’ve made a jump so this is rather late in the process. |
| 9 | 00:00:51,000 | 00:00:59,000 | They become untangled, untwisted, and gradually line up across the equator of the cell. |
| 11 | 00:00:52,000 | 00:00:55,000 | The cells were taken from the root of a Crocus plant. |
| 10 | 00:00:54,000 | 00:00:59,000 | This plate has had the amino acid, Tryptophan added to it. |
| 11 | 00:00:55,000 | 00:01:00,000 | You can see the chromosomes, now they become free in the cytoplasm. |
| 12 | 00:00:56,000 | 00:00:59,000 | We’re going to look at a film of dividing cells, but this time… |
| 11 | 00:01:00,000 | 00:01:04,000 | This plate, the medium in this plate has no Tryptophan in it. |
| 13 | 00:01:00,000 | 00:01:03,000 | ..taken from this plant here, the African Blood Lily. |
| 12 | 00:01:05,000 | 00:01:09,000 | Now I’m going to put cells from both cultures on both plates. |
| 14 | 00:01:05,000 | 00:01:07,000 | Both the Crocus and the Blood Lily has been chosen… |
| 10 | 00:01:06,000 | 00:01:12,000 | The centromere divides, freeing the chromosomes from each other. |
| 15 | 00:01:08,000 | 00:01:11,000 | ..because the chromosomes are large and easy to see. |
| 13 | 00:01:10,000 | 00:01:16,000 | Let’s mark the plates to start with so we know what we’re doing. |
| 12 | 00:01:10,000 | 00:01:13,000 | Here we are, here’s the same cell again. |
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