The correct answer is that the plants that grow them are actually clones. So instead of growing them from seeds, they're grown from cuttings, so from existing plants. So obviously the first seedless grapes were a plant that arose through mutation, that means that they don't have seeds. And some growers must have noticed this. And you can basically take a little shoot or a stem off the plant, dip it in rooting powder, put it in the ground, and a new tree will grow. This is how a lot of plants are cultivated now, and also a lot of seedless varieties. It's causing problems now with bananas though. Because they're all clones, they're getting struck down by funguses and things. If a population is genetically identical, it can very easily be wiped out because it has the same resistance to different pathogens.

When you take a pill like an aspirin or a paracetamol, what it does is to target the inflammatory cascade. What that means is that if you have an injury to a part of the body, you start to make substances in those parts of the body that signal to nerve cells that that part of the body is hurt and that you shouldn't move it around too much. The way the painkillers do it is they block this cascade of inflammation everywhere in the body at the same time so that anywhere that is hurting doesn't hurt as much. So it's not that it homes in purely on you headache; it has its effects everywhere in your body. But you only notice its effects where you had the pain before because it stops being so bad in that area.

I guess it's partly because the cold itself produces quite profound chemical changes in and around the nerves that report pain messages, and that's why anybody who's had cold hands for a long period of time will describe how intensely painful it is. So I suspect that it's because the nervous system is already in a sensitised state when one adds another signal to those nerves. What nerves do that aren't behaving properly is they misinterpret sensory information, and so my guess is that partly what's happening is that you've got nerves that have been upset by the cold and when you apply a warm stimulus, it might be interpreted as being painful. This doesn't necessarily mean that it's damaging. It may also be something to do with mixed signals going to the brain, so you have messages coming that they are very cold, but then you get a mixed signal about another sensation coming in. Often these signals can be interpreted as pain. I don't know if that's the right answer but that's what I would guess.

Well sherry's quite a rich source of alcohol. But I think it's got to be taken in the context of your overall sense of well being. Don't drink too much and make sure other aspects of your life are healthy. Unfortunately it doesn't contain the same specific healthy components that red wine does.

If you look at the way people eat and the length of time they live in the Mediterranean, this gives rise to a thing called the Mediterranean paradox, or the French paradox. People there seem to live a lot longer than they ought to because they eat very fatty food. But the fats that they do eat are of a certain type, things like olive oil. Olive oil is very rich in a type of fat called mono-unsaturated. When we talk about fats we talk about long chains of carbon atoms linked together. You can either have one bond between one carbon atom and the next, or sometimes you can have a double bond. And if you have lots of single bonds between them, then that's saturated fat, and it's bad for you. And the reason it's bad for you is that all the carbon chains can get very close together and stack up very neatly. This forms a very solid block of fat. It's not very chemically exciting and it clogs your arteries up. If you have things like olive oil, they have a double bond, which gives the chain a kink. So when you try to press oil molecules together they don't stack up very neatly. They don't form a solid block of lard, they're much more chemically exciting and this is why they're better for you.

The idea that you should have a low cholesterol diet to lower your cholesterol is completely flawed. In fact if you eat a low fat diet and have lots of refined carbohydrates, then your body likes to make cholesterol out of those excess carbohydrates. So a low fat diet isn't the secret to lowering cholesterol levels.

This is a reflex called the photic sneeze reflex and no-one's exactly sure what underlies it. We know that it's genetic and is passed on in families. About one person in four or one person in five is affected. People used to think that when you looked at the Sun, the bright light made your eyes water, the water ran down into your nose, tickled your nose and made you sneeze. This is not true because it happens too fast. What scientists think is that there's some sort of crossed wiring in the back of the brain where the size of your pupil is controlled, and that's what causes that to happen.

I think that polar bears are a lot faster than hippos, so that element of nimbleness would give it a great advantage. Although I guess if they got close enough, a hippo is a really vicious animal. I think that more people are killed by hippos in Africa than they are by lions and tigers and actual carnivores.

Smell molecules trigger nerve cells in your nose. These cells then connect to a structure called the olfactory tract and this links up to areas of the brain that are very close to where memories are laid down. This is in a primitive part of the brain, which controls animalistic behaviours such as emotions, sex drive and general arousal. So scientists think that smell can trigger all these other emotions. Also, memories don't seem to be laid down as a video clip, but are distributed all over your brain. So remembering something is like doing a jigsaw puzzle or a collage; the more pieces you have the easier it is to find more.

The correct answer is that the plants that grow them are actually clones. So instead of growing them from seeds, they're grown from cuttings from existing plants. So, obviously, the first seedless grapes were a plant that arose through mutation, that means that they don't have seeds, which some growers must have noticed and propagated.

To do this you take a little shoot or a stem off the plant, dip it in rooting powder, put it in the ground and a new tree will grow. This is how a lot of plants are cultivated now, and also a lot of seedless varieties.

That said, it's causing problems with bananas now: because they're all clones, they're getting struck down by fungi. If a population is genetically identical, it can very easily be wiped out because all the plants have the same genetic vulnerabilities. If a pathogen evolves to exploit this molecular loophole it's curtains for the crop because every plant is susceptible and the absence of sex means a lack of genetic variation.