Tuyển tập các báo cáo nghiên cứu về y học được đăng trên tạp chí y học Critical Care giúp cho các bạn có thêm kiến thức về ngành y học đề tài: On the nature of thumbs. | Minireview On the nature of thumbs Gunter P Wagner and Alexander O Vargas Address Department of Ecology and Evolutionary Biology Yale University Prospect Street New Haven CT 06520-8106 USA. Correspondence Gunter P Wagner. Email Published 3 March 2008 Genome Biology 2008 9 213 doi gb-2008-9-3-213 The electronic version of this article is the complete one and can be found online at http 2008 9 3 213 2008 BioMed Central Ltd Abstract Asymmetric regulation of Hox gene expression pre-dates the appearance of tetrapod digits and was co-opted in the development of thumbness . This asymmetric expression correlates with independent morphological evolutionary variation of digit I. Each finger on your hand is uniquely identified by its relative size position and shape. But on closer inspection only one digit is really different from the rest - the thumb digit 1 . Digit 1 has two bones phalanges whereas all the other fingers have three. Only the thumb can be moved away from the other digits a phenomenon called opposability and on a more subtle anatomical level growth of the corresponding metacarpal bone in the hand is proximal for the thumb but distal for all the other digits. In every respect the thumb stands out no pun intended as qualitatively different. With the appearance of a paper in Genes and Development by Montavon et al. 1 we now have a detailed understanding of some of the molecular mechanisms that make this anterior-most digit special. How is the thumb different The earliest trace of a difference between the future thumb and the other digits is the expression of a subfamily of Hox genes the AbdB-related group of Hox genes in the D cluster. Hox genes code for transcription factors and most jawed vertebrates with the exception of teleost bony fishes have the Hox genes in four tightly linked clusters called A B C and D 2 . Each gene cluster has the same 3 to 5 arrangement of corresponding genes with those determining .
