Essay --

Literature ReviewCan comparative modelling techniques successfully model an entire genome?Introduction there is a need of detailed description and understanding the expression and function of many proteins. Although the structure and function of protein is best memorized experimentally but it washbowl be predicted by comparative modelling (Sanchez and Sali, 1998). Homology modelling or comparative modelling is used to constructs a three-dimensional model of a protein by comparing its sequence similarity to one or more known structures of protein (Jacobson and Sali, 2004). Comparative modelling of protein structure is relevant to functional annotation of proteins based on structure and consequently enhances the impact of genome sequencing, functional genomics and structural genomics on medicine and biology (John and Sali 2003).The complete genetic information about amino acid sequences of different proteins is however provided us by genome sequencing efforts. We be now challenge d with assigning, understanding, controlling, and modifying the functions of various proteins encoded by these genomes. This task is generally simplified by native protein three-dimensional structures. The experimental methods used to determine the three-dimensional structures are X-ray crystallography and nuclear magnetic resonance (NMR) spectroscopy (Jacobson and Sali, 2004).These techniques have significant advances but unfortunately many protein structures are not soft accessible by experiments. The computational methods resolved the huge gap between the number of available sequences of amino acid and experimentally solved protein structures (Xiang, 2006). Over the pull through two years, in the comprehensive public databases, such as SwissProt/TrEMBL and GenPept... ...e than a factor of two (Vitkup et al., 2001). Alignment errors due to both their impact and frequency are the some important single limitation on comparative modelling. Conclusively, from the genome projects, c omparative modelling proficiently increases the value of sequence information while it is not heretofore possible to accurately model all proteins. The main holdups are the difficulties in detection of weak similarities for sequence structure alignment and for fold recognition and absence seizure of structurally defined members in many families of protein. Although only 400 domain folds out of the total of a few thousand are known so in the next ten years, the structure of most globular folds likely is to be determined. Therefore, comparative modelling possibly will be applicable to most of the domains of globular protein close to the completion of the human genome project.