Tuyển tập các báo cáo nghiên cứu về y học được đăng trên tạp chí y học Wertheim cung cấp cho các bạn kiến thức về ngành y đề tài: Conservation of tandem stop codons in yeasts. | Research Open Access Conservation of tandem stop codons in yeasts Han Liang Andre RO Cavalcantf and Laura F Landweber Addresses Department of Chemistry Princeton University Princeton NJ 08544 USA. ỶDepartment of Ecology and Evolutionary Biology Princeton University Princeton NJ 08544 USA. Correspondence Laura F Landweber. E-mail lfl@ Published 16 March 2005 Genome Biology 2005 6 R3I doi I86 gb-2005-6-4-r3I The electronic version of this article is the complete one and can be found online at http 2005 6 4 R3I Received 18 October 2004 Revised 12 January 2005 Accepted I6 February 2005 2005 Liang et al. licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License http licenses by which permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited. Abstract Background It has been long thought that the stop codon in a gene is followed by another stop codon that acts as a backup if the real one is read through by a near-cognate tRNA. The existence of such tandem stop codons however remains elusive. Results Here we show that a statistical excess of stop codons has evolved at the third codon downstream of the real stop codon UAA in yeasts. Comparative analysis indicates that stop codons at this location are considerably more conserved than sense codons suggesting that these tandem stop codons are maintained by selection. We evaluated the influence of expression levels of genes and other biological factors on the distribution of tandem stop codons. Our results suggest that expression level is an important factor influencing the presence of tandem stop codons. Conclusion Our study demonstrates the existence of tandem stop codons which represent one of many meaningful genomic features that are driven by relatively weak selective forces. Background In most organisms one of three stop codons UAA UAG
