This week we're exploring how populations come by their genes including the surprise finding of African DNA in a remote village in Yorkshire. Oxford University's Bruce Winney explains how studying rural populations in Britain is helping to uncover genes linked to different diseases, and Turi King, from Leicester University, discusses what your Y chromosome says about your surname. Plus we'll be hearing how Cambridge scientist Mike Majerus is putting evolution to the test with the help of the peppered moth, and in kitchen science, more jam tomorrow as Ben and Dave show you a trick with a rolling jar.
In this episode
Protein for plant petrol
As it looks like we'll be running out of oil in the not-too-distant future, scientists have been hunting for an alternative to fossil fuels for use in cars and other vehicles.
Some cars around the world are already running on ethanol, produced from crops such as corn. But it's expensive to make the fuel, and there are other environmental issues around the large-scale farming needed to produce the corn.
Instead, scientists are looking at breaking down cellulose, a sturdy chemical that makes up the tough cell walls in many plants, then fermenting it to produce ethanol. But breaking down cellulose isn't easy either, and requires the use of enzyme proteins.
Currently, the enzymes that have been used for breaking down cellulose aren't that efficient. But now researchers at Cornell University in the States have discovered a group of plant enzymes that could potentially produce ethanol from cellulose more efficiently than our current technologies.
This would make the process less expensive, and allow fuel to be produced from lower-grade crops, such as grasses or fast-growing trees.
The new enzyme was found in a tomato plant, and although more research is needed to find out exactly what it does, the researchers think might be involved in breaking down cell walls when tomatoes grow as they ripen.
The scientists also have evidence that similar enzymes exist in many other types of plants, which could be useful for making biofuels. For example, researchers might be able to breed fuel plants with high levels of these proteins, which would help to break down the cellulose in them and kick-start the fermentation process.
New planet discovered
In the constellation Libra, 20.5 light years away there is a star we call Gliese 581. This is a small rather dim star which astronomers have been studying for several years, and had found two large planets circling it. One at 15 times the mass of the earth orbiting every 5.4 days and another 8 times the mass of the earth orbiting every 84 days.
They are far too small to be detected directly by present day telescopes however they do make their presence felt. As they orbit they cause the star to wobble slightly. This movement changes the colour of the light given off due to the doppler effect which can be measured showing their presence.
Gliese 581 is a very dim star so although the closer planet is much too hot for water to be liquid the more distant planet is too cold. However Xavier Deflosse and a team from Grenoble have found another planet that is about right. This third planet orbits the star every 15 days is about 5 times the mass of the earth and is probably on average about -3°C to 40°C putting it in the middle of the habitable zone. This is the first planet we have found other than the Earth that could be in this temperature range.
However at 20 light years away we are unlikely to visit soon as this is about 20 million million km and it would take the fastest probe so far built about 37,000 years to get there.
Fighting both dandruff and epilepsy
It may not seem like an obvious treatment for epilepsy, but results from a team at Johns Hopkins Medical Institute have found that a chemical in anti-dandruff shampoo might be useful for treating the illness. Epilepsy occurs when nerve pathways in the brain "short-circuit", and nerves start firing off inappropriately. This is partly due to faulty behaviour on the part of potassium channels, proteins that help to calm down the firing of nerve cells by letting potassium flow out.
The researchers were studying these channels and tested thousands of chemicals to find ones that could boost the recovery and activity of the channels after they had been damaged. One chemical that proved quite effective in improving channel recovery was zinc pyrithione, the active ingredient in many dandruff shampoos. The chemical is just the right shape to slot into the channel and help potassium flow through. Lead researcher Professor Min Li suggests we can think of these channels as doors on the cell's surface, so the chemical makes the door both easier to open and stay open longer. He says "It's like a tunable hinge that helps sticky doors swing freely."
The team also looked at nerve cells grown in the lab, carrying a fault in their potassium channels that is also found in certain human epilepsy conditions. They found that the anti-dandruff chemical could also help boost the activity of the faulty potassium channels. As always, more work needs to be done, but this discovery could lead to improved treatments for epilepsy in the future.
You may remember at school someone being charged up by a Van de Graaf generator, and their hair standing on end because all the hairs now repel each other.
Engineers at Phillips may have come up with a way of using this principle to make a display out of fabric. The idea is to make a hairy fabric with the hairs a different colour to the base fabric. If the hairs are lying down all you can see is the hair colour. However if you charge them up and make them stand up, you are looking at them end on so you can see the different coloured fabric underneath. If a piece of fabric were split up into pixels and wired up appropriately you would have a furry display.
Why do geese fly in a V formation?
As a bird's (or aeroplane's) wing passes through the air, in order to hold itself up it creates a high pressure area of air below it's wing and a low pressure area above.
The air rushes up around the end of the wing and swirls around, creating a vortex behind each wing tip. This wastes energy for the bird in front but if a second bird flys slighty behind and outside the first bird, the air will be moving upwards. So it will actually give a bit of extra lift, for free, to the second bird, reducing the energy needed for flight.
Air will try and cancel this out by leaking around the end of the wing. This wastes energy and reduces the amount of lift the wing makes (this is why modern aircraft have vertical foils at the end of their wings to try and reduce this).
As flying at the front is more tiring than flying further back, migrating birds actually take it in turns to go at the front, so no one bird gets too exhausted.
Does junk DNA have a purpose?
It now seems that some of the 'Junk' is structural, helping to maintain of genes and chromosomes, and that some if it is very important for controlling how our genes work. There seem to be 'messages' coming from what was previously thought to be junk which help to control genes, turn them on and off and operate feedback cycles.There is some evidence that micro-RNA copied from 'junk' DNA may be essential in out immune system, and 'junk' DNA is now being studied for its effects in cancer.This is a quite a new field of research, so watch this space!
What makes a cake rise?
When making a cake you use baking powder or bicarbonate of soda, (or use self-raising flour, which already contains baking powder). Bicarbonate of soda contains carbon dioxide, which can be released as a gas by reacting it with acid or by heating. As the carbon dioxide is much bigger as a gas than it was in the bicarbonate of soda, it expands, makes bubbles in the cake mix and so makes the cake rise.Another way is to beat lots of air into things containing eggs, such as a soufflÃ©. As you cook the beaten eggs the air trapped in the bubbles expands, making the soufflÃ© rise. (The air bubbles contract again as it cools, which is why the soufflÃ© sinks!)
15:52 - Science Update: Consumerism
Science Update: Consumerism
with Chelsea Wald and Bob Hirshon
Bob - This week for the Naked Scientists, we're asking that age-old question, why do you buy what you buy? I'm going to tell you how the number of choices you have in front of you makes a difference, but first, Chelsea informs us that celebrities don't seem to have the power over our minds that some companies seem to think they have.Chelsea - We aren't sure if it was this way in the UK, but Catherine Zeta-Jones was once as synonymous with T-mobile in the US as its ubiquitous jingle. That is, until last year, when T-Mobile dropped her as its spokesperson, and said it would instead use everyday sorts of people in its ads. Well, new research from marketing professor Brett Martin of the University of Bath seems to vindicate that decision. His team found that people who buy products to impress others were more influenced by ads with so-called typical consumers than those with celebrities. Martin says this may be because the unknown spokesperson seems like someone you might actually meet and get a chance to impress.Brett Martin (University of Bath): What this means is that it may be more effective to spend less money getting typical consumers than more money on expensive celebrities.Chelsea - On the other hand, some of the nearly 300 volunteers had no interest in impressing anyone. They looked only at the product specs.Bob - Thanks, Chelsea. If you're opening an ice cream parlor, you might think it's better to offer sixty flavors than a measly six. But some studies have shown that consumers actually buy more when given fewer choices. To better understand this, Dartmouth College cognitive psychologist George Wolford and his students tried to sell up to twenty different kinds of black pens. Then they charted their sales success against the number of choices offered.George Wolford (Dartmouth College): We found that it peaked at ten, and went down on either side of ten, but we strongly felt that if you had other items, probably more complex items, we would expect it to peak at lower numbers. Bob - The findings demonstrate that more selection can, in fact, be a good thing up to a critical point. He says this probably applies not just to buying a TV, but also to choosing a career or even a spouse. Chelsea - Thanks, Bob. We'll be back next time with more science stories delivered with an American accent. Until then, I'm Chelsea Wald...Bob - And I'm Bob Hirshon, for AAAS, The Science Society. Back to you, O Naked Ones!
18:19 - The People of the British Isles
The People of the British Isles
with Bruce Winney, University of Oxford
Kat - I understand that you are carrying out a large project funded by the welcome trust which is trying to find out where the British people came from, what's in our genes. Can you tell me more?Bruce - That's right, we're looking to collect about 3,500 blood samples to collect DNA from people throughout the UK. We're then going to look at a lot of genetic markers to get a genetic map of the British Isles.Kat - What sort of markers are you looking for?Bruce - We're basically looking for markers which might give us differences between different parts of the regions, So some that are maybe more common in the North East than the South West, or vice versa. Typical ones that people might think of that we may look at are things like the ABO blood grouping system that most people know about; they're either: A, B, O or AB. There's another marker system which is involved in your immune response, so how you respond to pathogens and things and it's also involved in rejection of tissues and tissue typing. This is known as the HLA system, one of the most diverse genetic markers there are in humans. Another interesting one is called MC1L, the Melano-cortin 1 receptor. It's involved in skin colour and also associated with red hair. So genes involved in hair colour or skin colour might give us differences between different regions, so these are the sort of markers we're looking at.Kat - Where are you looking across the country?Bruce - We're looking throughout the UK but we're particularly looking for rural communities; we've actually got quite strict criteria. We're looking for people who have four grandparents born in the same area, a 30-40 mile radius. We're looking in rural areas rather than the major cities, because with places like Leeds, Manchester, Birmingham etc, over the last 500,000 years there's been a lot of movement and mixture of people into those cities from throughout the countryside and indeed throughout the world. So by focussing on rural areas, and by focussing on people who've got four grandparents born there; those volunteer's families are likely to have been there for many generations and will be good representatives of the area.Kat - So what do you think you're going to find? Are you going to be able to look back and say: "well, you're a Viking..." are you hoping to find that far back?Bruce - Well, there's various things we can do, we've done some preliminary analyses on a small number of samples and there's a couple of interesting things that come out of this. One is that there's a marker that's on the Y chromosome, the chromosome that defines maleness, and there's a particular version of that which is found in about 25% of Norwegians and then as you go further Eastwards along Northern Europe, it gets more and more common. It is also found in the Orkney Islands; 33% of men in the Orkney Islands have this version but in the rest of the UK and in most of the rest of Northern Europe it's actually incredibly rare. So here we have a very rare and unique but specific marker which is associated with the Norse Vikings. In general its actually a lot more complicated than that as this example isn't something that happens all the time but you can look at collections of genes and collections of markers and look at the frequencies in different places. We are beginning to show that we can see differences between the Celtic fringe, which represents the ancient Britons in the Neolithic times before the Anglo-Saxons came in, and also the Anglo-Saxons themselves. So we are beginning to look at historical differences.Kat - And I understand that as well as looking at where the populations have come from, there are health aspects. What other things can you find in our genes?Bruce - Well the main reason for doing this is from a medical point of view, which is why the Wellcome Trust have funded it. We're going to use this sample set to help us search for genes that make people susceptible to diseases and these are in particular the common diseases and the complex ones such as heart disease, cancer and mental health diseases. To understand how we can do that, you need to think about how researchers tend to do these sorts of experiments. A researcher might be working on diabetes and over the years she will have built up a collection of diabetes patients. She'll then get a group of people who don't have diabetes and look for genetic differences between the two groups. So anything that is more common in the group of patients is likely to be associated with the disease. So what we're doing is we are setting up what we call a UK control population so this is an average selection of people from throughout the UK that can be used in any of these sorts of studies for any of these diseases.Kat - So if people are interested in taking part in your study, tell us again what the criteria are and how can people find out more?Bruce - We are looking for people who have ideally got four grandparents born in the same area. By area I mean the same parish, county, 30-40 mile radius or something like that. And we're looking for rural areas so we are intentionally excluding the big cities such as Birmingham, Manchester and London. We are still recruiting. We have now got about 1900 of our samples and so we are still desperately looking for lots of people. If people are interested and they think they fit the criteria, or know people who might do, they can go onto our website, which is www.peopleofthebritishisles.org and there are details of who to contact and how to volunteer through that.Kat - Sounds great. So a lot of our listeners are in East Anglia so there might be a lot of rural populations there. So if there's anyone out in the fens listening... Where in the country have you managed to get people from so far?Bruce - Well, East Anglia's been very good for us, particularly Norfolk, we've just about got all the individuals we need from Norfolk but we're still looking for Suffolk. Other counties, Lincolnshire we have just about finished but basically every other county we are interested in so places like Cornwall, Devon, Oxfordshire, South Wales, North Wales, Cumbria and places in Scotland we are still actively recruiting. So basically anywhere in the country where there are rural populations, we are interested in hearing from people.Kat - Brilliant. So that's www.peopleofthebritishisles.org. Thanks very much, Bruce.
Why don't ducks get hypothermia?
Ducks have very little muscle in their feet, mainly tendons. This means that the muscle which makes them move is further from the feet and better insulated, and there's less in the feet to keep warm.
Ducks also have a clever circulatory system, where warm blood going down to the feet in arteries goes closely past the cold blood coming back from the feet in the veins.
This is called a counter-current heat exchanger, as heat is exchanged between the hot blood and the cooler returning, meaning that the birds do not lose too much heat through their feet, because the blood that reaches the feet has already surrendered most of its heat to the returning blood.
There is some suggestion that they also make an anti-freeze compound in their feet called ethylene glycol, which stops the blood in their feet from freezing by lowering it's freezing temperature. Natural anti-freeze chemicals are also often seen in fish that live in freezing waters.
27:51 - Surnames, Yorkshiremen and Y-Chromosomes
Surnames, Yorkshiremen and Y-Chromosomes
with Turi King, University of Leicester
Kat - Hi Turi, the last time I saw you was on TV! You were talking about this research looking at how genes are spread through populations and where we've come from, so can you tell us a little more about the study where you've found African genes in Yorkshire?Turi - That's right. Actually, what I've been doing has been part of a larger PhD project which was funded by the Wellcome Trust, it's been looking at the link between Y-chromosomes and surnames. The interesting thing that we're looking at here is that the Y chromosome is just passed down from father to son, and surnames are also passed down from father to son so you might think that there may be a link between a type of Y chromosome and a particular name. There are a lot of things which can break this link, the obvious one is illegitimacy, where you have one man's Y chromosome type but another man's surname, adoption will do the same sort of thing. The other thing is numbers of founders for a particular surname, so if you were to look into the surname 'Smith' there's going to be a number of different founders for that particular surname because it comes from 'Blacksmith'. You would expect a number of different Y chromosome types associated with that surname. If you look at rare surnames you find that quite often there's just a single Y chromosome type or just a handful associated with that surname. One of the surnames I looked at was Attenborough (as the two alternative spellings - Attenborough and Attenborrow), 87% of them, regardless of spelling variant, are descended from one individual. There are a handful of other Y chromosome types associated with the name, but we don't know if they are illegitimacies, adoptions or other founders who happen to have had fewer descendants.Kat - So tell us about the research in Yorkshire; you found a family, or people with a Yorkshire surname, and I understand they're a white population but they have African ancestry. How did you find that out?Turi - Originally, when I was just starting the PhD we put advertisements in local newspapers and about 421 men responded. I was typing their Y-chromosomes expecting to come across all the typical European ones you would expect to find and I came across this really unusual type. I showed it to my supervisor, Mark, and we thought that maybe we'd made a mistake, so we tested it more, and found out that it belongs to a really rare African Y chromosome type that's only found in West and North Africa and there's only 26 other cases of it in the world, all of which trace back to this confined space. So then we decided to look at the surname; are there other people with this surname who've got this Y chromosome type so I recruited another 18 men and 7 of them had this rare Y chromosome type. We knew they all had to be related, we just didn't know how, so we commissioned a genealogist to look at their family trees and they managed to trace two family trees back to 1788 and 1789 but they couldn't join them up. They all originated in Yorkshire and looking at the genealogical evidence and the genetic evidence they probably join up in the early 18th century. Kat - So how does this fit in with the history of black people in Britain? Where do you think this originally came in to the gene pool?Turi - Well there are a couple of really obvious routes, one is the Romans, as they had a garrison of Moors who were guarding Hadrian's wall in AD 200, so that's a possibility. More likely is the slave trade, as you had the first Africans arriving in this country in 1555. Again, West Africa is where a lot of the slave trade came from and with the sheer numbers of West Africans coming into the country as domestic servants you would expect that to be the most likely route.Kat - So where do you go from here? Do you have another project on the go already?Turi - Well I'm writing up a PhD at the moment! One of the other things that came out of the research was that because there's so much sharing of Y chromosome types within surnames, particularly rare ones, you can actually use a Y chromosome type to predict a surname. I did this as a small pilot study using 150 different surnames; I took 2 guys at random from around the country who had one of these surnames and I looked to see how often they shared a Y chromosome type and I found that, if you take two 'Smiths' at random they don't tend to share a type, but if you take two 'Revis' for example, then the chances of them sharing a Y chromosome type is actually quite high. So out of this small pilot project I found that I could predict, across the board, correctly using just the Y chromosome type 19% of the time I could predict the correct surname. If you just use the rare half of the surnames, the lower 75, it goes up to 34% accuracy. There's implications in this for using it as an investigative tool for the police, whereby they could put in a Y chromosome type collected from a crime scene and get it to bring out surnames, which could help with prioritising a list of suspects. It would never replace standard research, it's just an investigative tool as a way of prioritising suspect lists, but it could be quite powerful in terms of cutting investigation times.Kat - I think our Dr Dave, being an Ansell, has got quite a rare name...Turi - In fact, I've got my surnames dictionary here and so I can look it up! Ansell... English, chiefly East Anglia, from a Germanic personal name, composed of the elements Ans 'God' and Helm 'Protection' or 'Helmet', so 'Godhelmet'...Kat - I think we'll have to start calling Dave 'Godhelmet' from now on...Turi - I think you should! It was bought to France by a famous medieval churchman, apparently.Kat - Well we won't be able to do that with Dr Chris, because he's Chris Smith, so a common surname. But what else can Y-chromosomes tell us about populations, because obviously it doesn't work for women...Turi - No, it doesn't. It just tells you about the male half of the population, but it's quite a nice, compact piece of DNA which doesn't much from father to son so it gives you a nice clear record of our male ancestry. Like looking at markers such as M17 found in higher frequencies in Norway than elsewhere, its a nice way of saying; 'you've got a particular type of M17, so you have a higher chance of having ancestry from there.'
36:52 - The Evolution of the Peppered Moth
The Evolution of the Peppered Moth
with Mike Majerus, University of Cambridge
Kat - So you are, I suppose, a lepidopterist?Mike - Well I'm just a bug man, I do lepidoptera, and I also do ladybirds.
Kat - So tell us a bit about your work in Moths, what can they tell us about evolution...
Mike - well, I work with one moth in particular, a very famous moth, and then a couple of hundred other species which are very much less famous. These are the British Moths that have black forms, sometimes called melanic forms, and some of those only have had black forms since the industrial revolution. The most famous one is the peppered moth, the first black form of which was found in 1848 in Manchester. It spread very rapidly so within 50 years, by the end of the 19th century, 98% of the Mancunian peppered moths were black. There was a famous Victorian lepidopterist called Tutt who suggested in 1896 that the reason for that was because the tree trunks had all lost their lichens due to acid rain, and then soot fallout had blackened the tree trunks so the black form was harder to see on those trees. Birds therefore selected - naturally selected - the black form because they ate the other form which was white with black speckling.
Kat - So going back a bit, where would this black form have come from?
Mike - Just a chance mutation.
Kat - In one of the genes that are responsible for pigment?
Mike - The lepidoptera have lots of different melanic (pigment) genes, and this is just a particular mutation, a particular change in one of the wings which produces black all over the wings instead of just in a speckled pattern.
Kat - So once this had arisen randomly those insects weren't getting eaten so much, so then they could breed and so it would spread?
Mike - Yes, the idea is that this mutation would occur every now and then back over thousands of years, but usually it would be a disadvantage and so would be selected against. When the environment had changed, with pollution, then it became an advantage and so it spread.
Kat - I understand that some creationists say that the original experiments that were done to prove this, as a lovely example of evolution at work, something changing in the genes in response to the environment; but some people say that the results weren't very well done, or that it's inaccurate.
Mike - There's a very interesting lepidopterist called Bernard Kettlewell who, in the 1950s, did some classical experiments that are now reported in all the school textbooks. In two different woods, one polluted, one unpolluted, he released live moths of both white and black forms onto tree trunks. In polluted Birmingham he saw that birds took far more of the pale form, so the black form was more successful. Down in Dorset it was the other way round, so on trunks with Lichen the black from was eaten more often than the pale form. Since the 1950s scientists have gradually tinkered with Kettlewell's experiments, said he did it at too high density, he moved moths from one location to another and so on. So scientists have been saying this might not be absolutely accurate. About 10 years ago, the creationists started not only saying that these experiments weren't valid, but some were actually saying that Kettlewell faked his results, he was accused of fraud. Unfortunately both Bernard Kettlewell and his mentor E. B. Ford, who also has come in for a lot of criticism from the intelligent design and creationist people, are both dead. I decided that because there's so much criticism (if you put Peppered Moth into Google, there's actually more hits on creationist websites that on biological websites, that just seems to be the wrong way round) so since 2001 I've been doing a new predation experiment in which I'm trying to correct for every single one of the flaws that people have pointed to in the way Kettlewell did it. Actually, peppered moths don't usually rest on tree trunks; they rest underneath lateral branches, in the shadows. I put them in the right place, I let them, within a limited arena, choose their own resting sites. They can fly at night and choose where to rest, so I'm not telling them where they've got to sit, they do it themselves and so on. Unfortunately, this takes a tremendous amount of time because I have to do it at the density that the moths occur in nature. So I can only do rather few per day, but I'll finish this year, thank goodness! Hopefully, that will either say that Kettlewell is wrong, in which case I'll probably get the front page of the Times and Nature, or it will turn out that he was right and then I hope some of the critics of Kettlewell and Ford would then admit that they were wrong. Although given that if you prove one thing, creationists tend to just move the goalposts, which is why we now have this strange thing 'Intelligent Design', so I really doubt that we will change anyone's mind. What I'm really trying to do is say that the peppered moth case is or isn't a good example of Darwinian Evolution in action, and try to keep creationists out of science class.
Kat - That's a subject for a different show I think, but lets talk more widely about insect populations and how they respond to the environment. Are there other examples of how insect populations have changed, are we seeing populations changing as climate is changing?
Mike - Yes, populations change, whether this is actually affecting the genes so much... One of the strange things, that many people who think about evolution don't quite understand is that there's a huge difference between somewhere like Galapagos, where Darwin made many of his observations, and 'us'. By 'us' I mean Britain connected to continental Europe until a few thousand years ago, and the great continents. If climate is changing what will happen here, and in Europe, Asia and connections to Africa, is that things will simply move. They move first, they adapt second. If they can move they will simply move, so what we're really seeing is a lot of southern European species coming up here and being able to survive.
Kat - We've had questions about Ladybirds that are black with red spots, but aren't they traditionally red with black spots?
Mike - We have three native species that are always black with red spots, the Pine ladybird, the Kidney Spot and the Heather ladybird. We have two other species, the Two-Spot and the Ten-Spot, that sometimes are black with red spots but they can also be red with black spots, or orange with black spots. That's one thing I'm working on because they're polymorphic, a bit like us having black or red hair, that's all genetically controlled. There's also a new one, the Harlequin ladybird which arrived in 2004 and is now spreading like mad, taking over from out native ones. We need to study that because as it's just arrived we can study all sorts of things as it's having to adapt to the British climate and other environmental factors. Unfortunately, although it's beating all our native ladybirds already, its going to get even better at doing it, so goodness knows what's going to happen in the next fifteen years.
46:36 - Racing Jam Jars - Kitchen Science Pt2
Racing Jam Jars - Kitchen Science Pt2
with Dave Ansell & Derek Thorne, the Naked Scientists
Join Dave and Derek for the results of this week's Kitchen Science experiment...