ABSTRACT
In the past five to six years, gene mapping and complete genome sequencing projects poured out an immense amount of genetic information. In parallel, increasingly effective methods have been developed to analyse the sequence data and genes functionally. Despite all of this, there is still more sequence information that we are unable to explain. We can determine the Open Frame Readings (OFRs), the sites of supposed genes, and the introns and exons, but there are limited tools for deciphering the rest. With the help of comparative genome analysis we can predict some regulator regions, which are known in some species but unknown in others. The predicted genes and regulatory elements need to be validated functionally. There are two distinct ways to characterise a gene or a regulatory region and test its function by gain of function assays in vivo. Tissue culture systems allow a fast and cheap way of characterisation. But their in vitro nature is a disadvantage: these systems are unable to mimic the processes of a complex organism. The other way is to insert the gene or the regulatory region back into an animal and analyse its expression in a whole living system (i.e., in vivo).
