Nearly the whole of my research career took place in the present ‘golden age’ for the study of DNA, genes and genomes. At the end of the 1960s scientists had indicated how useful it would be to be able to isolate individual genes in order to study their structure and function. That wish was fulfilled in the spin-offs from the invention in the early 1970s, of genetic modification (genetic engineering), a scientific milestone that marked the start of this golden age.
By the end of the 20thcentury experiments were being done, that thirty years earlier were not even dreamed of. This was certainly true in my research group’s work on the biochemistry and genetics of DNA replication, giving us the real privilege of uncovering some of the beautifully complex and intricate mechanisms used by cells in ‘managing’ and copying their genetic material. Continue reading →
One of the people who set Charles Darwin along the road to evolutionary theory was not a scientist, but the Governor of the Galapagos Islands, Nicholas Lawson. When Darwin and the Beagle crew landed on Charles Island, Lawson invited him to dinner. As they talked, Lawson mentioned that the giant tortoises for which the Galapagos chain was named varied noticeably between islands. In fact, said Lawson, if any tortoise was brought to him, he could identify which island it came from.
It turns out that the tortoise-naming party trick was not exclusively Lawson’s. Whether he was just repeating what the locals said, or had actually studied the tortoises personally, the fact remains that the person who set Darwin on the course of studying variation among species on the Galapagos islands was not a scientist.
John Bryant, the author of last week’s guest post, told this story during his lecture at this year’s Faraday Summer course, and I enjoyed it because Continue reading →
Children love to watch caterpillars turn into butterflies, and scientists are no less fascinated by this process. I have mentioned biologist John Bryant’s contribution to the science and faith discussion on this blog a number of times. In this guest post, he writes about his sense of wonder at the processes he studies.
I have been fascinated by the natural world for as long as I can remember, and that fascination led to a career in biology. As a professional biologist my main focus has been the way DNA works as genes, and especially the processes by which DNA is replicated prior to cell division.
Regular readers of this blog will know of the excitement, awe and wonder I have Continue reading →
The scale of the universe is truly mind-boggling, and it’s worth dwelling on. But it’s important to keep looking in other directions. Every day your body produces millions of new cells without you even thinking about it. Each of your cells contains the same set of DNA instructions*. Your cellular DNA quota (genome) is an incredibly thin chemical chain with about 6 billion links called nucleotides, and is approximately 2 metres long** (don’t test this at home!) Each time a new cell is produced, that DNA has to be copied to an extremely high level of accuracy. It was the same for all 30 or so trillion cells in your body – it all started with DNA replication.
When a cell is about to divide, a number of proteins recognise and bind to the DNA at specific points. Geneticist John Bryant has said that it’s harder to begin DNA replication than it is to start a nuclear war – the process is that tightly controlled. At least forty different proteins have to be in position before replication can begin.
Once initiated, DNA replication happens relatively quickly. The clue to how this works is in the iconic DNA double helix image that is represented in art and architecture the world over. DNA consists of two complementary strands twined together: one is a mirror image of the other. This helix is unwound, and each chain is used as a template to build a new complementary strand of DNA.
When you were conceived, you received a copy of each of your parents’ DNA. Making DNA is like writing: without proper editing mistakes will undoubtedly slip in. For DNA replication, multiple layers of proofreading ensure a high level of accuracy. So out of your 6 billion inherited DNA chain-links, only 30-70 of the links are wrongly copied. That’s a maximum of one mistake in every 100,000,000***. If I could do anything that accurately I’d be very happy! And this is all happening at great speed: 6 billion chemical reactions often in less than 24 hours.
I remember writing about DNA replication in great detail during an exam at university. At the end of my essay I waxed lyrical about how this process was happening incredibly fast, at such a high level of accuracy, and without any conscious effort on our part. I’m not sure what the person marking my exam thought about my reverie, but I was impressed!
I often find that looking in detail at the universe – even just standing outside on a dark night – gives me a feeling of smallness. Staring at the stars, or studying cosmology in depth, has given some people an awareness that there might be a God out there after all. What does looking at the very small and complex make people think? Tiny packages like cells or atoms can contain surprisingly complex systems, and immense power. Nothing is as simple as it seems. Perhaps as biology proceeds over the next few decades we’ll hit up against similar philosophical questions to those raised by the older sciences of physics and astronomy.
As a biologist I have seen some very beautiful things. My own area of research was eye development and genetics in the small tropical ‘zebrafish’. Every developmental biologist tends to love the organism they work on, and I was no exception! Continue reading →