ABSTRACT
As with genome annotation, attempts to determine the functions of unknown genes are made by computer analysis and by experimental studies. The basis of homology searching is that related genes have similar sequences and so a new gene can be discovered by virtue of its similarity to an equivalent, already-sequenced gene from a different organism. Homologous genes are ones that share a common evolutionary ancestor, revealed by sequence similarities between the genes. An easily overlooked but nonetheless vital aspect of genome annotation is the need to have an agreed and consistent terminology with which to describe the functions of different genes. Computer methods for assigning functions to unknown genes are becoming increasingly sophisticated, but the bioinformatics approach has limitations and cannot identify the function of every new gene that is discovered in a genome. Devising experimental methods for functional analysis of new genes is proving to be one of the biggest challenges in genomics research.
