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: Large-scale assignment of orthology: back to phylogenetics? | Review Large-scale assignment of orthology back to phylogenetics Toni Gabaldón Bioinformatics and Genomics Program Center for Genomic Regulation Doctor Aiguader 88 08003 Barcelona Spain. Email tgabaldon@ Published 30 October 2008 Genome Biology 2008 9 235 doi gb-2008-9-10-235 The electronic version of this article is the complete one and can be found online at http 2008 9 10 235 2008 BioMed Central Ltd Abstract Reliable orthology prediction is central to comparative genomics. Although orthology is defined by phylogenetic criteria most automated prediction methods are based on pairwise sequence comparisons. Recently automated phylogeny-based orthology prediction has emerged as a feasible alternative for genome-wide studies. Homologous sequences - that is those derived from a common ancestral sequence - can be further divided into two different classes according to the mode in which they diverged from their last common ancestor 1 . The divergence of two homologous sequences by a speciation event gives rise to orthologous sequences whereas a duplication event will define a paralogous relationship between the duplicates. Although such straightforward definitions could suggest that distinguishing paralogs and orthologs is simple it is definitely not. For example it is not unusual for multiple lineage-specific gene loss or duplication events as well as other evolutionary processes to result in intricate scenarios that are difficult to interpret. Far from being a simple curiosity the establishment of correct orthology and paralogy relationships is crucial in many biological studies. For instance phylogenetic analyses that aim to infer correct evolutionary relationships between several species should be based on orthologous sets of sequences 2 . Moreover as orthologs are relative to paralogs more likely to share a common function the correct determination of orthology has deep implications for the transfer of functional information across .
