It is easy to observe that some people are happier than others. But trying to explain why people differ in their happiness is quite a different story. Is our happiness the result of how well things are going for us or does it simply reflect our personality? Of course, the discussion on the exact roles of nature (gene) versus nurture (experience) is not new at all. When it comes to how we feel, however, most of us may think that our happiness
The post Is happiness in our genes? appeared first on OUPblog.
Knowledge that we all have DNA and what this means is getting around. The informed public is well aware that our cells run on DNA software called the genome. This software is passed from parent to child, in the long line of evolutionary history that dates back billions of years – in fact, research published this year pushes back the origin of life on Earth another 300 million years.
The post The magic of Christmas: it’s Santa’s DNA appeared first on OUPblog.
By Bianca Haase
Cats are among the most common household pets and they share the same environment with humans and thus many of the risk factors. Obesity is a growing problem for feline health for the same reasons as it is in humans and has become a serious veterinary problem. Multiple diseases, such as type II diabetes mellitus and dermatosis, are associated with excess body weight and obesity in cats and may result in a lowered quality of life and potentially lead to an early death. Appleton et al. demonstrated that about 44% of cats developed impaired
This is the second post in our latest regular OUPblog column: SciWhys. Every month OUP editor and author Jonathan Crowe will be answering your science questions. Got a burning question about science that you’d like answered? Just email it to us, and Jonathan will answer what he can. Today: What are genes and genomes?
By Jonathan Crowe
I described in my last blog post how DNA acts as a store of biological information – information that serves as a set of instructions that direct our growth and function. Indeed, we could consider DNA to be the biological equivalent of a library – another repository of information with which we’re all probably much more familiar. The information we find in a library isn’t present in one huge tome, however. Rather, it is divided into discrete packages of information – namely books. And so it is with DNA: the biological information it stores isn’t captured in a single, huge molecule, but is divided into separate entities called chromosomes – the biological equivalent of individual books in a library.
I commented previously that DNA is composed of a long chain of four building blocks, A, C, G, and T. Rather than existing as an extended chain (like a stretched out length of rope), the DNA in a chromosome is tightly packaged. In fact, if stretched out (like our piece of rope), the DNA in a single chromosome would be around 2-8 cm long. Yet a typical chromosome is just 0.00002–0.002 cm long: that’s between 1000 and 100,000 times shorter than the unpackaged DNA would be. This packaging is quite the feat of space-saving efficiency.
Let’s return to our imaginary library of books. The information in a book isn’t presented as one long uninterrupted sequence of words. Rather, the information is divided into chapters. When we want to find out something from a book – to extract some specific information from it – we don’t read the whole thing cover-to-cover. Instead, we may just read a single chapter. In a fortuitous extension of our analogy, the same is true of information retrieval from chromosomes. The information captured in a single chromosome is stored in discrete ‘chunks’ (just as a book is divided into chapters), and these chunks can be read separately from one another. These ‘chunks’ – these discrete units of information – are what we call ‘genes’. In essence, one gene contains one snippet of biological information.
I’ve just likened chromosomes to books in a library. But is there a biological equivalent of the library itself? Well, yes, there is. Virtually every cell in the human body (with specific exceptions) contains 46 chromosomes – 23 from each of its parents. All of the genes found in this ‘library’ of chromosomes are collectively termed the ‘genome’. Put another way, a genome is a collection of all the genes found in a particular organism.
Different organisms have different-sized genomes. For example, the human genome comprises around 20,000-25,000 genes; the mouse genome, with 40 chromosomes, comprises a similar number of individual genes. However, the bacterium H. influenzae has just a single chromosome, containing around 1700 genes.
It is not just the number of genes (and chromosomes) in the genome that varies between organisms: the long stretches of DNA making up the genomes of different organisms have different sequences (and so store different information). These differences make sense, particularly if we imagine the genome of an organism to represent the ‘recipe’ for that organism: a human is quite a different organism from a mouse, so we would expect the instructions that direct the growth and function of the two organisms to differ.
B
By Jonathan Crowe
What links a queen honeybee to a particular group of four atoms (one carbon and three hydrogen atoms, to be precise)? The answer lies in the burgeoning field of epigenetics, which has revolutionized our understanding of how biological information is transmitted from one generation to the next.
The genetic information stored in our genome – the set of chromosomes that we inherit from our parents – directs the way in which we develop and behave. (We call the attributes and behaviours exhibited by an organism its ‘phenotype’.) Traditionally, the genetic information was thought to be encoded solely in the sequence of the four different chemical building blocks from which our DNA is constructed (that is, our genome sequence). If a DNA sequence changes, so the resulting phenotype changes too. (This is why identical twins, with genomes whose DNA sequences are identical, look the same, but other individuals, whose genomes comprise different DNA sequences, do not.) However, the field of epigenetics opens up a strong challenge to this traditional view of our DNA sequence being the sole dictator of phenotype.
So what actually is epigenetics? In broad terms, epigenetics refers to the way that the information carried in our genome – and the phenotype that results when this information is ‘deciphered’– can be modified not by changes in DNA sequence, but by chemical modifications either to the DNA itself, or to the special group of proteins called histones that associate with DNA in the cell. (It’s a bit like taking a book, with a story told in the author’s words, and adding notes on the page that alter how the story is interpreted by the next person to read it.)
But what has epigenetics to do with the group of four atoms, the one carbon and three hydrogen atoms mentioned at the start of this blog post? These four atoms can combine to form a methyl group – a central carbon atom, with three hydrogen atoms attached; the addition of methyl groups to both DNA and histone proteins in a process called methylation is a primary way in which epigenetic modification occurs. For example, the addition of a methyl group to one of the four chemical building blocks of DNA (called cytosine, C) either when it appears in the sequence CG (where G is the building block called guanine) or the sequence CNG (where N represents any of the four chemical building blocks of DNA) appears to result in that stretch of DNA being ‘switched off’. Consequently, the information stored in that stretch of DNA is not actively used by the cell; that stretch of DNA falls silent.
But what of our queen honeybee? Where does she fit into our story? A queen honeybee has an identical DNA sequence to her workers. Yet she bears some striking differences to them in terms of physical appearance and behavior (amongst other attributes). These differences are more than just skin-deep, however: the pattern of methylation between queen and worker larvae differs. Their genomes may be the same at the level of DNA sequence, but their different patterns of methylation direct different fates: the queen honeybee and her workers develop into quite distinct organisms.
Things take an interesting turn when we consider the cause of these different methylation patterns: the diets that the queen and workers experience during their development. The queen is fed on large quantities of royal jelly into adulthood, while worker larvae face a more meager feast, being switched to a diet of pollen and nectar early on. It is these diets that influence the way in which the queen and worker bees’ genes are switched on and off.
It is not just the queen honeybee whose genome is affected by the environment (in her case, diet). Mice exposed to certain chemicals during pregnancy have be
By Cassie Ammerman- Publicity Assistant
Richard Dawkins is the bestselling author of The Selfish Gene and The God Delusion. He’s also a
pre-eminent scientist, the first holder of the Charles Simonyi Chair of the Public Understanding of Science at Oxford, and is a fellow of New College, Oxford. Called “Darwin’s Rottweiler” by the media, he is one of the most famous advocates of Darwinian evolution. His most recent book is The Oxford Guide to Modern Science Writing, a collection of the best science writing in the last century.
This is the first in a series of podcasts we’ll be running from an interview with Richard Dawkins. In it, Dawkins talks about the different scientists he chose to include in The Oxford Book of Modern Science Writing. In this selection, Dawkins talks with Dorian Devins about James Watson and Francis Crick, the two men famous for discovering the structure of DNA.
Transcript after the jump.
DORIAN DEVINS: Francis Crick is one of the people in here, and I know you…
RICHARD DAWKINS: Yes, I met him a couple of times. I know Jim Watson rather better. Francis Crick died a couple of years ago. He was of course the other half of Watson and Crick, and they were both indispensable. It’s a wonderful illustration of how two people coming together seem to make something that’s greater than the sum of their parts. Francis Crick has written a number of books. He’s always very thoughtful, very stimulating. It’s impossible for him to say anything that isn’t interesting, and he was one of the great, possibly the greatest, intellects of the molecular biology revolution, which started with Watson and Crick in 1953, when they were both young men. But Crick went on to in a way dominate the field. I mean, in the elucidation of the genetic code, the fact that it’s a triplet code, for example, he played a leading role in that. So he became a kind of elder statesman of molecular genetics, and then rather later in his life, he switched completely to a totally new field, which was the study of consciousness. And he was never really a proper neurobiologist, but he sort of somehow managed to well, use his eminence in the field to open doors to talk to neurobiologists. And once again, he was a very, very thoughtful, stimulating figure in that field, as well as his own field of molecular genetics.
DEVINS: Whereas I guess Watson, more or less, stuck to genetics, although he did…
DAWKINS: Yes he did stick with genetics, and Watson was pretty much involved in initiating the human genome project. He didn’t stay in the human genome project, but he was largely responsible for getting it started in the first place.
DEVINS: And their writing styles are so different. It’s interesting.
DAWKINS: Yes, well, that’s right. Watson’s writing style is amazingly readable, but very odd. I mean, it’s…any teacher of English would blue-pencil it straight away. He had a most weird tendency to stick strings of adjectives before a—not so much adjectives, more phrases that count as adjectives—so he’ll say, if he wants to say he walked by, well quite close to here is Keble College (which is the Victorian building designed by Butterfield), Watson will say “I walked by the Butterfield-designed Keble College.” Sticking an adjective, making a phrase into an adjective, and then sticking it before the noun. And it’s an odd way of writing, but for some reason, it’s very readable, and I find that his books are page turners in a way that any teacher of English would sort of veto.
DEVINS: It’s funny how the personalities come out in the writing sometimes.
DAWKINS: Yes, that’s true. I think it’s part of the personality, and I think it’s because Watson writes in such an irresponsible way. He doesn’t mind who he offends, and so you’re always kind of turning the page, waiting for the next bit of scandal really.
DEVINS: As he is in life.
DAWKINS: Yes.
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Here's a quick crunkin' Santa pic for the holidays!
Cheers!
Mike.
www.wandelmaier.com
