Go Forth and Multiply: How Y-Chromosomal Adam and Mitochondrial Eve spread their DNA to every currently living human

There are seven billion people alive today. The bible has been telling us for over a thousand years that every one of them is descended from just two humans, Adam and Eve. It’s interesting how often old stories we used to explain our world before science can strike a grain of truth! DNA that is passed from father to son on the Y chromosome, and mitochondrial DNA that is inherited from one’s mother, can both be traced back to single points of origin. As our understanding of population genetics in the world today grows, we get closer and closer to identifying our last common ancestors.

eveil

This is the best bio-biblical pun you will see today

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23andMe: With Big Data comes Big Responsibility

23andMe – the home genetic testing company backed by Google – have announced they want to use their data for drug development. I think this is a great idea, but a very important time for Google to remember their “Don’t be evil” policy.

What is 23andMe?

23andMe offer mail-order personal genome sequencing: you’re sent the kit, you take a swab of DNA from inside your cheek, send it back and wait for a copy of your own blueprints to appear online. What an age to live in! The data comes in the form of a ‘SNP panel’, meaning it tests for a long list of known single nucleotide changes that are common in the general population. The unique pattern of SNPs you have inherited can show you your ancestors paths across the world, as well as identify some nasty diseases you may carry or be predisposed to.

A South-African colleague of mine took one of the tests for fun. He was pleasantly surprised to find that the family rumour that his great-great-great grandmother was black were true, and that his whole family had inherited some of her black-african SNP pattern. He took great pleasure in announcing this at a family gathering, in front of some unpleasant racist relatives. Nothing annoys bigots like scientific proof that they’re ideas are bad and they should feel bad!

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PRDM9: My Favourite Gene

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.

Pearson Scott Foresman, donated to the Wikimedia Foundation

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?

recombinationz

Recombination: The process by which two chromosomes swap chunks of DNA with one another

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3 Bodyparts I Would Totally Splice Into Myself

Do you ever get bored with your generic kidneys and garden variety human eyeballs? I know I do. While there are a couple of good decorative and useful mods out there (I’ve opted for piercings and fillings), we are all looking forward to the time when we can just splice in whatever we fancy. Here are three interesting alternatives and extras I wouldn’t mind having:

Statocysts (Squid ears)

Squid have a really neat auditory system – who knew? Well, no one until recently – we only just discovered that they have a sense of hearing at all. Research on the Loligo pealei species has revealed that they hear using nifty organs called Statocysts which, like human ears, help with balance as well as detecting sound.

By IllaZilla (Own work) [CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0) or GFDL (http://www.gnu.org/copyleft/fdl.html)], via Wikimedia Commons

These Longfin Inshore Squid are listening to Reel Big Fish and there is absolutely nothing you can do about it

Statocysts are little hollow balls. They are filled with liquid and the inside surface is covered with tiny hairs, each of which is linked to a nerve. Within the void of the statocyst floats a tiny grain of calcium called a statolith. The statolith normally rests near the front of the ball touching a few hairs. Any sound waves that reach the squid cause the statolith to jiggle about and touch different hairs. The brain interprets the pattern of nerve activity this produces and ‘hears’ the noise! Like humans, the squid can get an idea of the direction from which the sound is coming from by comparing the time of detection and the strength of the vibration reported by each statocyst.

A Statocyst

A Statocyst

If that wasn’t enough, the statocyst regulates balance. If the squid moves forwards quickly the statolith jumps from the front of the cyst to the back. The delay between the front and back hairs being activated, as well the position of the activate hairs report the direction and velocity of the movement. In the same way the squid gets feedback about whether it has moved up, down, left or right.

Squid ears are probably no better than human ears, but I would definitely have a pair – cephalopod over Ipod, as I always say.

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IT CAME FROM SPACE: Celestial Events and Terran Extinctions

Space is a hostile and chaotic place, and yet on our little rock, life – as Richard Attenborough famously said – finds a way. Unless a gentle shift in stellar fortune BRUTALLY DESTROYS IT.

We know about the threat of comets, aliens, the inevitable nova-ing of our star and the eventual heat death of the universe, but space also has some more subtle tricks…this post explores one of them.

Two million years ago a slightly underwhelming marine extinction event occurred: fossil evidence shows a mass death of molluscs and Plankton which is considered to be the marker between the  Pliocene and Pleistocene epochs. What puzzled palaeontologists who studied this extinction was that it occurred in conjunction with a spike in levels of the iron isotope 60Fe in the sediments where these fossils were found. Were the extinction and the isotope related?

Phytoplankton By NOAA MESA Project (http://www.photolib.noaa.gov/bigs/fish1880.jpg [1]) [Public domain], via Wikimedia Commons

Phytoplankton By NOAA MESA Project (http://www.photolib.noaa.gov/bigs/fish1880.jpg [1]), via Wikimedia Commons

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