Searching the unknown with gene trapping.

dramatic increase in sequence information, both in the form of complementary DNA (cDNA) and genomic DNA, has created a huge gap between the discovery of genes and the process of identifying gene function. To fill this gap, the 'gene-trapping' approach has been developed; this combines into a single process the three stages of gene cloning, the study of the pattern of gene expression and the analysis of the respective mutant phenotype. Recent results indicate that gene trapping can be used successfully to clone specific genes that are involved in the development of the central nervous system, limbs and haematopoietic system. Continuous improvements in the design of trapping vectors, faster sequencing of cDNA clones and more-efficient in vitro pre-screening will certainly aid the large-scale trapping of mammalian genomes.