Daily Archives: February 5, 2009

Charles Darwin and the Rain Forest

i-483a35d54b9f564228dc98196d965c2f-rain_forest.jpgThe first time I read the following passage from The Voyage, I was reminded of my own first experience in a rain forest (in Zaire, not Congo). Evident in this passage is at least a glimmering of Darwin’s appreciation for the complexity of ecosystems. Darwin could be considered the first scientific ecologist.

But enough of my commentary … this passage very much stands on it’s own …
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Study on voluntary vaccination reveals interesting complexities

ResearchBlogging.orgWhen word of this study gets around, you may start to hear that voluntary vaccination “works.” This would not be an accurate statement. There is a new study just now out in PLoS Computational Biology that reveals that under certain conditions, which may actually be quite rare, voluntary vaccinations might lead to the eradication of a disease (contrary to ‘popular wisdom’). However, you must realize that the study has some important limitations and the results do not suggest that most (if any) current vaccination issues be voluntary rather than mandatory.

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Mutation Patterns in the Human Genome are More Variable Than Expected

I want to bring your attention to a somewhat dense and possibly inconclusive (but important) paper accompanied by a very informative overview in PLoS Biology, concerning mutations in the human genome.

ResearchBlogging.orgMutation rates and patterns of mutation are important for a number of reasons. For one thing, the genome itself is a data set that is both broad and deep. There is a lot of information in a given individual genome (a haploid set of genes from a person, for instance) but there is a wide range of variation in that information. So, inferences or assertions regarding the nature and distribution of genes or their variants cannot really refer to a single version of the genome, but must also take into account the variation in DNA sequences.

A very obvious area where variation is important is in reconstructing phylogenies. “Family trees” of populations or species can be reconstructed by estimating the genetic difference between pairs of samples, and from this, estimating the amount of time that has passed between a Last Common Ancestor and each of two later populations. These dyads (or triads, depending on how you count them) can then be pieced together to get a phylogeny … a graph representing the historical divergence of populations or species … that tells us a particular version of history. Obviously, the rate of mutation must be known or assumed to make this work. Variation in mutation across the genome, or across a population, or across the structure of the family tree itself will cause incorrect inferences.

The research paper is “Cryptic Variation in the Human Mutation Rate” by Hodgkinson et al. Here’s the key finding:

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Link Between Vitamin D Deficiency and MS

ResearchBlogging.orgMultiple sclerosis (MS) is the most common serious neurological disease that affects young adults, wiht about 2.5 million victims worldwide. The disease involves a loss of myelin in brain and spinal cord neural tissues. Myelin is the protective and insulating layer that covers most axons in the mammalian nervous system.

can be caused in part by a particular set of genetic variations in the Major Histocompatibility Complex (MHC), which in turn cause significant neurological effects. There is compelling epidemiological information to suggest that there is also an important environmental factor. The present study makes the argument that vitamin D deficiency, especially during pregnancy and early development, is one such important environmental factor.

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