Mendel's peas genetics - Experiments that changed the world.

This is the story of the father of genetics, a neurotic Moravian monk called Gregor Mendel. Johan Gregor Mendel, who would solve the mystery of inheritance, was born in this house in 1822. It's in an obscure village called Mtsitsa, now in the Czech Republic. Mendel's father was a peasant farmer who grew mainly fruit. The family were poor and depended on these trees for their livelihood and food. Learning about plant breeding and growing was essential for survival. Later, it would form the cornerstone of Mendel's scientific work. Mendel was an extremely bright child, which put terrible pressure on his parents. They scrimped and saved so they could send him to a decent school. But money was a constant worry. Mendel, being a sensitive youth, felt a strain. He was ill three times and had to return home to recover. And it seems quite clear that these illnesses were psychological. I mean, they were breakdowns. And I think when he was living away from home and studying, he felt under a great deal of pressure to return. He must have had a great streak of stubbornness. And despite the breakdowns, he sort of picked himself up and got on with his own ambition. In his late teens, disaster struck for Mendel. His father was crippled in a farm accident. Tradition demanded that sons step into their father's shoes. But the young Mendel was too delicate and sickly a youth to be any good at running a farm. Instead, he took a fateful decision. This is how he put it. It is impossible for me to endure such exertion any further. I am compelled to enter a station in life that would free me from the bitter struggle for existence. I have requested and received admission to the Augustinian Monastery of St. Thomas's in Bruner. Being a member of the Augustinian Brotherhood suited the young Mendel perfectly. The order encouraged its members to educate themselves in science as well as theology. Food and shelter were guaranteed. And the quiet contemplative life matched Mendel's personality. Only one thing bothered him. In the course of Mendel's pastoral duties, he used to visit the local hospital. And he found that experience extremely distressing. He found the idea of human sickness and suffering extremely distressing, so much so that he actually had to be taken off that duty. Freed from this part of his religious duties, Mendel discovered another feature of the monastery. In its grounds was a small botanical garden. It was little more than a collection of a few Moravian flowers. But it would transform Mendel's life. He said, In my free time, I occupy myself with the small botanical collection at the monastery. I have become so addicted to the study of nature, I will shrink from no exertions to fill the gaps in my knowledge. Mendel became more and more interested in the variety of life. Why species are different from each other, and what makes members of the same species vary. As well as his fascination with plants, Mendel's interests took a morbid turn. He was also very interested in the whole matter of human deformity, human versions of what the botanist called sports, mutations. Therefore he was actually sort of strung between these two things, decided anxiety and faced with sickness and a fascination, because he was obviously very interested to know where these deformities came from. In Mendel's day, people knew about sperm and eggs, but had no way of explaining how they actually combined to produce the next generation. The most popular theory of inheritance held that at conception, a mother and father somehow merged, making their child a blend of the two of them. Professor Steve Jones, one of the country's top geneticists, explained why this so-called blending theory was so appealing. It seems clear that somehow you're a mixture, an average of what your parents were. If your father was very tall and your mother was very short, you'll be somewhere in the middle. The way that must work, it seems, is perhaps they mix their blood together or mix some fluid together in some way. Everybody believed that because it's obvious, but it's obvious and it's wrong. This is the kind of thing that really got farmers and breeders worried about blending inheritance. Here we've got a classic case of a black sheep and a family. Here's the two parents, the mother and the father. They're nice and white, or off-white, as they're rather city-side sheep. And this is what they had, which is utterly different. Now, there's no way you can make that black sheep as a kind of blend of those two. That black sheep, you can be absolutely certain, somewhere in the family line of these two guys, there's been another black sheep. And if you carry on for long enough, another one will be born. How far back might it be before the black one comes up? Well, sheep don't keep very big pedigrees, unfortunately. But it could be two generations, ten generations, or a hundred generations. Really? But it doesn't work with blending. That couldn't possibly work. It's got to be something different. Another problem with blending theory apparently resides under my hat. Now, when did your hair start falling out? Be honest. Well, about the age of 17 or 16. And it was all gone by the way, 23, 24? I don't know, I had it a bit until I was 26. Well, 26, oh, I didn't mean to interrupt you. Let's say, maybe someday you might have some grandsons, okay? It's quite likely that some of those grandsons, well I could give you some pretty definite probabilities, some of those grandsons will be bald. Now, supporters of blending theory couldn't explain why my kind of baldness, the kind that strikes early, often appears in the children of pursuit fathers. Or how a nectarine can grow from a peach seed. Or how two blue badges can mate and produce a pure white child. So that's what killed the idea of blending, these throwbacks, the way in which parents could produce children that were nothing at all like themselves, but a bit like a distant ancestor. Something else was going on, and you needed a genius to find it out. Very simple, and that genius was Mendel. By the 1850s, Mendel's pastoral duties had him teaching science at a school in Bruno. Earlier, his scientific curiosity had taken him to Vienna, where he had studied physics and math, as well as botany and natural history. Mendel soon found himself having to teach bogus theories of inheritance, like blending. The curriculum also included the even more antiquated idea that each sperm is a complete miniature person, and the egg is just there to give it food. Even some of the 12-year-olds here spotted flaws in this idea. They might have the woman's eye, and it could be a boy, but it's got part of the man and the woman, so it couldn't be that way. Wow. Come up here. Come up here, two. Come right up here. All right? Let's really celebrate, number two. I want you to stand up here, all right? Oh, sorry. Up here. Up here, all right? I'd like you to hold this as if it's some kind of glorious thing, all right? This is like a prize, okay? Okay. He's got a great future in science. Give that man a hand. In these years, in the mid-1800s, every accepted idea on biology was about to be overturned. In England, Charles Darwin, fresh from his trip to the Galapagos Islands, was developing his theory of evolution by natural selection. Meanwhile, in Bruno, Mendel was about to embark on a journey of his own, one that would explain something Darwin never could, how evolution actually works. A host of disparate ideas were coming together in Mendel's mind. His observations of the natural world were leading him to a revolutionary way of thinking about inheritance. Where he got this idea from, I suspect, is not biology at all. It was from physics. It was from physics and mathematics. The thing about mathematics is that you do not have blending. You've got numbers. And Mendel was obviously a very competent mathematician. He was a demonstrator in the physics department in Vienna University. He obviously was very able in physics. And I think this gave him the way in. Mendel reasoned that if mathematics could unlock the secrets of physics, surely it could tell us something about biology, about life itself. But to do this, he needed a living thing with observable characteristics that were easy to count. Enter, with fanfare, onto the scientific stage, the humble pig. It was exactly here, in this monastery garden, the Augustinian Monastery of Bruno, that Mendel had his 35 metre by 7 metre pea patch. This is back in 1856. Along here, you can see the foundation of Mendel's greenhouse, which he used for accelerating his pea growing process, as Mendel was going to be growing thousand upon thousand upon thousand of peas. Mendel's mighty pea extravaganza took eight years and involved about 30,000 plants. With the help of the biology department at Manchester University, I'm going to have a go too. Mendel was trying to understand how certain characteristics pass from one generation to another. Peas, for instance, come either smooth or wrinkly. Mendel planted a greenhouse full of peas, half from a smooth pedigree, half from a wrinkly. He then let them grow. This is Bob Callow, a plant biologist. He's talking me through the hardest bit of Mendel's experiment. I have to crossbreed each plant that grew from a smooth pea with a plant that grew from a wrinkly one. It's incredibly fiddly. The reproductive organs of a pea are modest to say the least. I've got it open. That tiny thing. Oh, well, it's so tiny. Mendel had to collect tiny grains of male pollen from one pea flower and stick them under the female bits of another. How long would it take Mendel per flower to do this? Well, it depends how expert he was. It would take me about half an hour to do the whole thing. Mendel must have done this thousands of times. He must have had the patience of Jones. After two weeks, this pollen and egg combo turns into a pea pod. These peas, all smooth wrinkly hybrids, would take the world one crucial stage closer to modern genetics. Blending theory, the dogma of Mendel's day, would have predicted that a pea born of one wrinkly and one smooth parent would look like an average of its parents. So what would these hybrids actually look like? Amazingly, every single pea that these crossed plants have produced is smooth. And if we look at all these, you see we've taken some of these ones out from the other pods, and all these are smooth peas. So the wrinkly character has completely disappeared. Though these peas had one smooth and one wrinkly parent, they looked smooth. What had happened to the information, the factor that had made one of their parents wrinkly? Had it vanished? Mendel planted all these smooth peas. What they did next would change the world. We need a little bit more out of you. By 1860, Mendel was about halfway through his experiment and beginning to act peculiarly. Excuse me, this is, uh, not exactly what we're looking for, is it? Visitors reported that he referred to his peas as his children. After a few months, the smooth peas born of hybrid wrinkly-smooth parents were fully grown plants. Mendel now let them self-fertilize. Peas do this because they have both pollen and egg in the same flower. The big question now was what sort of baby peas would the smoothies produce? Now something truly amazing happened. As if from nowhere, wrinkliness was back. Three smooth, three wrinkled. What's the significance of that? The real significance, even from this pod, is first of all that the wrinkled character is reappearing, and secondly that we've got two different types of peas in the same pod. So we've got some segregation. This is this recessive character, which everybody thought had disappeared forever, which Mendel has shown has re-emerged, if you like, in the grandchildren. So the factor for wrinkliness existed in the smooth parent without showing itself. But why had it reappeared in some of its children? To find out, Mendel did something only a mathematician would. One, two, three, 1241. He counted exactly how many of the peas were smooth and how many were wrinkly. This took a while, because he had 7,324 peas to count. 5,400, 5,474 smooth peas. Nearly 6,000 of them were smooth, like their parent. Just under 2,000 were wrinkly. It was a ratio of almost exactly 3 to 1. He was a superb teacher, because he thought so much further beyond that ratio. What's a 3 to 1 ratio? What could be more boring than a proportion of one quarter of wrinkled peas? But from there, he worked out the absolute fundamentals of life, which is that life is based on particles, units, that you can't actually see, that are hidden away, and can come together and move apart. And that's the discovery of the whole of genetics. It all turns on that one stroke of illumination. Mendel realized that if a pea contains both smooth and wrinkly factors, half the pollen it produces will contain the smooth factor, the other half the wrinkly. The eggs will be similarly divided. During reproduction, there are exactly four ways in which pollen and egg can combine. Smooth with smooth. Smooth with wrinkly. Wrinkly with smooth. Wrinkly with wrinkly. But Mendel knew any pea with a smooth factor would always look smooth, because the smooth factor dominated. So only wrinkled, wrinkled pears would actually look wrinkled. This explains why there would be three times as many smooth as wrinkled peas. In February 1865, Mendel paced nervously, awaiting to address the Bruno Society for Natural Science. In his briefcase was the explanation for how inheritance worked. How we get black sheep from white, nectarines from peaches, and why my grandsons might end up bored. In it was the first step to dolly the sheep. The meeting was a disaster. The audience expected a talk on plants. What they got was a maths lecture, full of ratios and incomprehensible formulae. ...at the full number of the classes of the series by the combination of the expression... ...and therefore in themselves constitute the expression... ...characters of the hybrid... ...plus small a. The minutes inform us there were neither questions nor discussion. The audience just left. A new science was born and no one noticed. Mendel's results were dismissed as at best of interest to people who worked on peas. Maybe the rules that applied to peas didn't apply to humans or to mice. Nobody ever thought that there would be a fundamental unity in biology. So that somebody who wasn't interested in peas wouldn't have interest in Mendel. And that's probably why he was dismissed. Three years after his forgotten lecture, Mendel was elected abbot of the monastery. Although he did continue some experimental work, he soon became embroiled in another maths problem. A row about the monastery's tax bill. It was a relatively minor matter but the stubborn streak in his character... ...that had driven him to grow and count peas for eight years... ...meant it took over his life. He became obsessed by his battle with the authorities of taxation. So much so that there was a time when the brothers were trying to get him... ...well, almost committed as unstable. They were obviously very concerned about the way he was approaching this problem. He offered no compromises whatever. Mendel became a rather sad old man. Still dreaming of the glory he would never get. He said, Though I have suffered some bitter moments in my life, my scientific work has brought me a great deal of satisfaction. And I am convinced it will not be long before the whole world acknowledges it. Sixteen years after he died in 1884, the world finally acknowledged Mendel's genius. English and Dutch botanists discovered and verified his work. And a statue was unveiled in his honor in Bruno. The particles of inherited information he discovered were named genes. And people soon realized that they were common to all life on earth. The shy Moravian monk had changed the world. And next Sunday at 7, Ken recreates the experiments of Michael Faraday, the bright spark behind electricity. And for the booklet of the series, send a cheque for $3.50, payable to Channel 4, to the six experiments that changed the world, P.O. Box 4000, Manchester M60, 3LL. It can improve your performance. In Gibraltar, the archaeologists continue searching for answers to the mystery of why the Neanderthals disappeared. By the time they're done, they will have sifted through 27 tons of sediment, stopping for each tiny clue. The bones can't tell us everything about these people. We can reconstruct their anatomy. We can look at the way their muscles were working. We can measure the size of the brain and the shape of the brain case. But what we don't have is any clue about the wiring of that brain. To get answers to those kind of questions, we have to look at the behavior. We have to flesh it out with the archaeology. In one of the Gibraltar caves, the team has uncovered clues to how the Neanderthals lived. The residue of an evening spent here, eons ago. Well, a number of things have come up that have been really intriguing. Number one, I suppose, is this hearth, a little fireplace. In a little bowl-shaped depression, you have got charcoals and other materials that are carbonized. And what appears to be the case here is that we have got a hearth that may have been used for one night. Now, elsewhere in the cave, we have other examples of areas that were occupied for probably equally short periods of time. Neanderthals are often credited with taming fire. And now, after thousands of years, the ashes give up clues to how they used it. With Neanderthals, we have spreads of charcoal, where they're living amongst their own refuse, amongst the bones of the animals they've butchered. They probably come into the cave, find a relatively warm spot, maybe against the wall, they construct a fire, but they don't really organize their activity around it. They're not sitting around it telling stories or whatever. Higher up in the same cave, the team has located a more recent fireplace.