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Dating Mammalian Evolution

Fri, 28 Mar 2014 15:14:37 +0000

When the age of the dinosaurs ended around 65 million years ago, mammals stepped in to fill the gap, and the age of the placentals began. However, whether early placental mammals were already present on Earth before the demise of the dinosaurs has been the subject of a long standing debate. Recent research in GEE [...]

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The Delicate Balance of Effect and Response

Tue, 18 Feb 2014 11:50:36 +0000

We may not always be aware of it, but many wild plants, animals, fungi and even bacteria, provide crucial services to us which keep the ecosystems of Earth functioning. Environmental changes caused by human activities are now threatening many species, and those that cannot withstand these changes may be lost forever, potentially taking the services [...]

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It’s All in the Wrist

Fri, 20 Dec 2013 16:18:20 +0000

The evolution of the primate wrist has been dramatic, enabling primates to adapt to a wide variety of lifestyles and walking styles, including tree-swinging, climbing and terrestrial walking both on four legs and two. In hominids, the evolution of the bipedal gait freed up the forelimbs for tool use, and the wrist evolved independently from [...]

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The Transcriptional Profile of A ‘Wingman’

Wed, 27 Nov 2013 14:25:48 +0000

In many species, males have special adaptations to attract females. From antlers to stalk-eyes, to bright plumage and beards, males across the animal kingdom work hard to look attractive to the opposite sex. In some species, looking good isn’t enough, though. Male wild turkeys need a less attractive ‘wingman’ to help him attract a woman. [...]

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Damage and Fidelity: The Role of the Female Germline in mtDNA Inheritance

Mon, 11 Nov 2013 15:13:12 +0000

Billions of years ago, one single-celled organism engulfed another, beginning a symbiotic interaction that would change live on Earth forever. The mitochondria are what remains of this symbiotic event, and are responsible for producing energy in all eukaryotic cells. Derived from a free-living organism, they carry their own genes, but these genes are at risk [...]

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Mitochondria and the great gender divide - GEE's Profs Andrew Pomiankowski, Rob Seymour and Dr Nick Lane and Zena Hadjivasiliou publish paper in Proceedings of the Royal Society B

13 December 2011

8 December 2011

Eukaryotic cells

Why are there two sexes? It’s a question that has long perplexed generations of scientists, but researchers from UCL have come up with a radical new answer: mitochondria.

Using a new mathematical model, the team led by Dr Nick Lane and colleagues from the UCL CoMPLEX, and the Research Department of Genetics, Evolution and Environment showed that inheriting mitochondria from only one parent – in effect, the ‘female’ – improves fitness by optimizing the interactions between the two genomes. The paper is published today in Proceedings of the Royal Society B.

Dr Lane said: “The difference between the sexes boils down to the need to keep fit when energy demands are high”.

Descended from free-living bacteria, mitochondria were swallowed whole by another cell between one and a half to two billion years ago. But despite being engulfed, these tiny power packs have retained their own tiny genome, encoding just a handful of proteins, all of which are necessary for generating energy in the cell. 

The strangest thing about this odd arrangement is that cell respiration relies on proteins encoded by two genomes, the tiny mitochondrial genome and the nucleus, where most DNA is stored. For respiration to work properly, the two genomes must work together to encode proteins that interact with nanoscopic precision. 

"This difference seems to be the deepest evolutionary difference between the two sexes" - Zena Hadjivasiliou

Zena Hadjivasiliou, a PhD student in CoMPLEX and first author of the paper, said: “A clue to the answer was found in simple single celled organisms called protists. These tiny creatures normally have two sexes, despite the fact that it is impossible to tell them apart even with an electron microscope. 

“The only real difference between these ‘sexes’ relates to mitochondria, the tiny power packs found in all complex cells. In simple protists, one sex passes on mitochondria, the other does not,” added Hadjivasiliou. 

While the model shows that two sexes are only borderline necessary in simple cells like protists, but by the time large, energetically demanding organisms had evolved, two sexes made a big difference to maintaining fitness. 

Hadjivasiliou said: “This difference seems to be the deepest evolutionary difference between the two sexes. As a result all the gender wars throughout nature ultimately stand on this pinhead.”

Image: Altmann's Bioblasts - The four seasons (Credit: Odra Noel)

Links

Nick Lane
Energy revolution key to complex life
UCL’s Nick Lane wins the 2010 Royal Society Prize for Science Books
Research in Proceedings of the Royal Society B
UCL CoMPLEX
Research Department of Genetics, Evolution and Environment

Page last modified on 13 dec 11 12:16