Tag Archives: mutation

One mutation every day

At least some people believe that once it’s published in Nature, it’s superior science – even when it’s rather trivial (or even wrong). There is a category “Brief Communications Arising” but when you are trying to get your comments there you will get this message by email:

In the present case, while we appreciate the interest of your comments to the community, we do not feel that they challenge key data or conclusions of the papers by Pleasance et al., and therefore we cannot offer to consider your paper for publication in our Brief Communications Arising section.

Pleasance et al. is a recent paper accompanied by a press release that tells you Continue reading One mutation every day

How we inherit acquired traits – all about non random mutations in the human genome

This is just a material collection for a forthcoming review. I am collecting links to studies showing an increased mutation rate in CpG islands that may possibly fix gene activation status. Continue reading How we inherit acquired traits – all about non random mutations in the human genome

Evolution in fast motion

Nature genetics as an advance online publication about comparative genome sequencing of E. coli where 13 de novo mutations in 5 strains were monitored over 44 d (or ~660 generations). It is a great study – not only because the author list includes one of my previous coauthors – but for giving a first insight about development of a mutation and fixing its allele frequency. Unfortunately, there is no flowchart and the methods are somewhat vague, what has been sequenced (or resequenced) in which strain at what time . In other words who are the winners? Did they manage that by their own strength or with a little help of some friends? Why rises the allele frequency always to 100% and what about some discrepancy of allele frequency and fitness? We will hopefully see more of these studies, yea, yea.

Genetics making up of Homo sapiens

Lets start a further workup of the evolutionary thread. With the complete human and chimp genome on our harddisks we are now able to compare genome sequence and genome activity of both species. A 2003 review by Sean Carroll summarizes our pre-genome knowledge about pan and homo lineages 6 Million years ago. The most interesting question is which mutations or genome rearrangements (Popesco 2006) are most relevant in the separation of lineages.

BTW I have still doubts about any positive effects of mutations (although this might be possible). Yes, I wonder also where are the exact pan-homo transitions (although the Sahelanthropus tchadensis might be a good candidate). Furthermore, I have doubts in survival of the fittest where non-survival of the non-fittest seem to be more relevant ;-) “Survival of the Sickest” is a CD of Mad Sin and a book of Sharon Moalem 2007.

Neuroanatomy might have provided some clues of a larger frontocortex in homo sapiens although the detailed cytoarchitecture could be as relevant. Noise of neutral substitutions could have confounded previous findings. It is also not clear to me if expansions and contractions of whole gene families are even more relevant. We may also renember that most quantitative traits have a polygenic background.

In any case FOXP2 could be associated with speech and language disorders (Vargha-Khadem 2005) where another prominent gene was now found in the 49 regions that are different between chimp and human but otherwise conserved (Pollard 2006). This new gene called “HAR1” is even expressed in the developing neocortex making it a prime candidate for species differentiation. Is there anybody able to convince me that the 18 fixed mutations in HAR1 have indeed a beneficial effect on brain development? A “leading edge” comment in Cell argues that all substitutions are upgrades from weak to strong base pairing:

Curiously, this weak-to-strong substitution bias in HAR1 extends over 1.2 kb, a region far larger than HAR1 itself. Such changes which also appear to characterize the HARs as a group undoubtely serve to strengthen RAN helices against dissociation…

I would also like to mention that male humans share more identity with male chimps than with female humans, at least on a genetic level, yea, yea.

Addendum

Even blogs have a half-life of less than 1 week. A new PNAS paper by Michael Oldham shows a more integrated view of human brain evolution by examining gene coexpression networks in human and chimpanzee brains. This seems to be another promising approach.

Ethnographic studies at Oktoberfest

Having many years of experience with ethnographic studies at Oktoberfest München, I am fascinated by a new Cell paper that shows distinct behavioral responses to ethanol. This is something that I alread assumed (although I did not known about this particular RhoGAP18B isoform only about ADH deficiency). Will the knowledge of more and more mutations in the lifestyle area raise ethical problems? Yea, yea.