tailieunhanh - Báo cáo y học: "The tree of one percent"

Tuyển tập các báo cáo nghiên cứu về y học được đăng trên tạp chí y học Minireview cung cấp cho các bạn kiến thức về ngành y đề tài: The tree of one percent. | Opinion The tree of one percent Tal Dagan and William Martin Address Institute of Botany University of Dusseldorf D-40225 Dusseldorf Germany. Correspondence Tal Dagan. Email Published I November 2006 Genome Biology 2006 7 II8 doi gb-2006-7-I0-II8 The electronic version of this article is the complete one and can be found online at http 2005 7 I0 II8 2006 BioMed Central Ltd Abstract Two significant evolutionary processes are fundamentally not tree-like in nature - lateral gene transfer among prokaryotes and endosymbiotic gene transfer from organelles among eukaryotes. To incorporate such processes into the bigger picture of early evolution biologists need to depart from the preconceived notion that all genomes are related by a single bifurcating tree. Evolutionary biologists like to think in terms of trees. Since Darwin biologists have envisaged phylogeny as a tree-like process of lineage splittings. But Darwin was not concerned with the evolution of microbes where lateral gene transfer LGT a distinctly non-treelike process is an important mechanism of natural variation as prokaryotic genome sequences attest 1-4 . Evolutionary biologists are not debating whether LGT exists. But they are debating - and heatedly so - how much LGT actually goes on in evolution. Recent estimates of the proportion of prokaryotic genes that have been affected by LGT differ 30-fold ranging from 2 5 to 60 6 . Biologists are also hotly debating how LGT should influence our approach to understanding genome evolution on the one hand and our approach to the natural classification of all living things on the other. These debates erupt most acutely over the concept of a tree of life. Here we consider how LGT and endosymbiosis bear on contemporary views of microbial evolution most of which stem from the days before genome sequences were available. A tree of life When it comes to the concept of a tree of life there are currently two main camps.