Gee Research Blog
The Importance of Size in the Evolution of Complexity in Ants
Tue, 16 Sep 2014 10:14:37 +0000
Ants are amongst the most abundant and successful species on Earth. They live in complex, cooperative societies, construct elaborate homes and exhibit many of the hallmarks of our own society. Some ants farm crops, others tend livestock. Many species have a major impact on the ecosystems they live in, dispersing seeds, consuming huge quantities of […]
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Understanding Catfish Colonisation and Diversification in The Great African Lakes
Fri, 05 Sep 2014 10:29:42 +0000
Why some regions or habitats contain vast, diverse communities of species, whilst others contain only relatively few species, continues to be the subject of scientific research attempting to understand the processes and conditions that allow and adaptive radiation. The Great African Lakes exist as freshwater ‘islands’, with spectacularly high levels of biodiversity and endemism. They […]
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Sex Differentiation Begins During Early Development
Wed, 27 Aug 2014 14:04:57 +0000
Males and females look different from each other, and these sexual dimorphisms are the result, largely, of sex differences in the expression of certain genes. Typically, scientists have studied sexual dimorphism in sexually mature adult animals, as this is the lifestage where differences are most apparent. However, many sex-specific phenotypes arise from sex-biased development, so […]
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Extinction and Species Declines:Defaunation in the Anthropocene
Mon, 18 Aug 2014 10:35:52 +0000
We are in the grips of a mass extinction. There have been mass extinctions throughout evolutionary history, what makes this one different is that we’re the ones causing it. A recent review paper from GEE’s Dr Ben Collen discusses the current loss of biodiversity and suggests that our main concerns are species and population declines, […]
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Defaunation in the Anthropocene appeared first on GEE Research.
Evolving Endemism in East Africa’s Sky Islands
Fri, 08 Aug 2014 14:16:32 +0000
The World’s biodiversity is not evenly distributed. Some regions are hot spots for species richness, and biologists have been trying better to understand why these regions are special and what drives evolution and diversification. A recent paper by GEE’s Dr Julia Day and recent PhD graduate Dr Siobhan Cox, investigated the diversification of White-Eye Birds […]Read more...
13 May 2013
"Why does selection care about codon usage (or what really determines ribosome velocity)"
Date & Time:
||Wednesday, 22 May at 5pm|
|Venue:||Medical Sciences AV Hill Lecture Theatre (map)|
Jurg Bahler (51602)
Owing to the structure of the genetic code more than one codon can specify the same amino acid. At first sight natural selection should not care which of the multiple synonymous codons is employed as the translated protein will be the same regardless. That we see selection on codon usage is thus intruiging. Understanding why selection cares about codon usage is important for understanding how cells work and, in turn, for understanding how to intelligently engineer transgenes. I provide evidence that selection cares about codon usage because it minimizes errors: it ensures translation is accurate and, in mammals, it ensures splicing is accurate. It is also commonly assumed that, because common codons match common tRNAs, codon usage must affect ribosomal velocity. Using ribosome protection data I find no evidence that in normal conditions codon usage has any effect on ribosomal velocity. In retrospect this result makes sense as the original logic was flawed - it considered only tRNA supply, not codon driven tRNA demand. We expect evolution to drive towards supply:demand equilibrium at which point rare codons specified by rare tRNAs wait as long to be translated as common codons specified by common tRNAs. More generally, we see little or no evidence for RNA mediated effects on translational velocity (either codon usage or mRNA structure). This leaves the problem of what does actually determine ribosomal velocity. I show that positively charged amino acids entering into the negatively charged ribosome exit tunnel have a profound effect on ribosome velocity. This can explain the evolution of the polyA tail. Methods to improve transgenes are suggested by these results.
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