PRDM9 is my favourite gene. Why? Because it is the strongest driver of speciation identified to date. Thanks to the activity of PRDM9 (and probably some other similar genes we haven’t recognised yet), we live in a world full of awesome metazoans such as hedgehogs, dragonflies, narwhals and axylotils. The gene was tricky to find and it’s function is still not completely understood. Here, I will explain the story of it’s discovery, what we think it does, and why that’s awesome.
PRDM9 was only identified quite recently by scientists trying to understand the process of genetic recombination. [Recap paragraph!]: In my last post I spoke at length about how chromosomes can swap pieces of DNA with one another during cell division. I mostly talked about ‘non-homologous recombination’, where two chromosomes swap non-matching pieces of DNA with one another, one chromosome often completely losing vital genes and it’s counterpart gaining extras. Non-homologous recombination often causes disease, so why haven’t we evolved out of it? The reason is that homologous recombination – where two chromosomes swap like-for-like stretches of DNA – is an integral part of evolution, as it allows species to ‘shuffle’ different variations of genes and see which combinations work best together. The question is, what controls recombination? How does it happen?
Recombination: The process by which two chromosomes swap chunks of DNA with one another
Mutation is usually considered to be a random, uncontrolled process: Mistakes during replication cause random changes to the DNA sequence, which may have positive, negative or neutral effects on the organism’s survivability. Positive changes are sustained, negative mutations die off, neutral mutations just float about. Mounting evidence now suggests that mutation can also happen on a far grander scale than this, that the changes are not always randomly located, and that they may not be mistakes at all.
Evolution is not content with changing a species one base at a time: mutation can actually cause huge genetic changes over just a single generation. Whether these changes are adopted by the whole species (becoming ‘fixed’) is another matter, but it seems that rather than progressing via a gentle trickle of subtle changes, species try out all these small mutations in different combinations, shuffling their genomes about like a deck of cards.
Although I was unjustly robbed of victory in the I’m a Scientist – Get Me Out of Here! Science communication challenge a few weeks ago, I did get to field a lot of great genetics questions from schoolkids. I would say about 80% of them related to the acquisition of mutant superpowers. Most mutant superheroes have powers beyond the scope of what you can achieve through mutation in the real world. On the other hand, some super traits actually do crop up occasionally, and others would definitely be achievable with a little dabbling…
Powers you can’t have
Powers causing really complicated modifications (like X-Man Angel’s wings) are a no-go because they would require a whole new set of genes working in harmony. Whole new neural subroutines and developmental changes could be necessary, making this a tall order to fill. This is not something you can acquire through a random mistake. Genetics is also cruelly shackled to the limits of physics, space and time. This rules out many of the cooler powers possessed by the likes of Storm, Cyclops and Polaris. Most of the bigshot superheroes spend a lot of their time bitching about the burderns of their powers anyway, so maybe it isn’t that great a loss to us after all.
Powers you can have:
All sorts of weird mutations crop up naturally all the time. In most cases they are debilitating – it’s far more likely that a typo in a computer program will mess it up rather than make it more efficient, and it’s the same with genes and proteins. A useful aspect to these mutations is that they tell us what a now broken gene was supposed to be doing in the first place, which can be very hard to figure out otherwise. Once we know what a gene does – be it from an animal or a human – we can start meddling. As all the hand-wringing Daily Mail readers out there tell us, the inevitable result of genetic meddling will be ‘designer babies’. Most of us are pretty on board with the current scope of this: procedures such as selecting for an egg cell which isn’t affected by a horrendous genetic disease from an affected/carrier mother, fertilizing it and re-implanting it by IVF to make a nice healthy child. Really though, why should we stop there? What kind of person would go to the trouble of making a designer baby that didn’t have super awesome mutant powers?? How else are you supposed to guarantee that your kid is better than all the other little screamers? Sure, you could make them tall and blue eyed if you want, but that’s so unimaginative. Therefore, allow me to present my catalogue of totally achievable mutant superpowers you can give your designer baby, mostly from the X-Men universe.
(If you can think of any other series with a good stock of supermutants comment it up and I’ll add them in)
I’m A Scientist – Get Me out Of Here!
Supported by The Wellcome Trust
This week’s blog post has been delayed while I participate in ‘I’m A Scientist – Get Me Out Of Here!’ a science communication competition in which schoolkids batter one with questions about science and life as a scientist. It’s been great fun but quite intense! Here are a couple of my favourite questions so far and my answers to them (pretty much all of which are about gene therapy):
Find me in the Bioinformatics zone! Blogging should resume next week!
Sponsored by The Genome Analysis Centre (TAGC)
Most genetic diseases are the result of a mutation that means a particular protein is made incorrectly, or not made at all. The idea of gene therapy is to infect cells – just how a virus would – with a small amount of DNA containing a replacement copy of the affected gene which slips into the cell’s genome and starts making the missing protein. The principle is elegant, but many challenges stand between the theory and successful use of gene therapy with real patients. In the last few years a number of advances have been made that have the potential to make gene therapy – something the medical community almost gave up on a decade ago – a powerful tool which could treat or even cure tons of diseases. What could be cooler than using the very tools viruses like HIV have painstakingly evolved to infect us with for our own benefit?
That’s right: I made a GIF: Genes are strings of bases within your DNA that contain the code to make different proteins. If a mutation occurs in the gene and changes the sequence of letters, it can change which protein subunits the cell uses to make the protein. This creates a mutant protein which may not function corrrectly, ot may stop the protein being created at all
Your DNA says way more about you than a finger print, cigarette stub, boot print outside the window or any of the other evidence Sherlock Holmes always found so informative. DNA testing has been a great boon for criminal investigators, but is it always compelling evidence? Here are some notable occasions where the silver bullet that is DNA evidence has got jammed in the barrel of the gun of justice and messed everything up:
“Oh no, my justice gun!”