A strategy using a genetic construct that is a kind of mutagen that acts as a cellular marker. If the construct integrates into a gene that is transcribed in a specific cell type at a specific time, the marker will be expressed in those cells at that time. In essence, it disrupts genes throughout the genome by inserting a DNA element that typically contains a ‘reporter’. This insertion usually mutates the gene. This technique evolved to overcome one of the shortcomings of classical genetics: it relies on the disruption of a gene leading to a recognizable or overt phenotype (and thus the function of the corresponding gene), but not all genes can be identified by mutagenesis. There are two reasons for this. First, many genes are functionally redundant (referred to as junk’), and share many other genes that may not be related at the sequence level (e.g., the use of genetic knockouts have revealed that a marked percentage of genes in yeast have no overt phenotype when disrupted). Second, many genes function at different stages of development, and so if they become mutated then it can have a lethal outcome or they can be highly pleiotropic thus masking the role of particular gene in a specific pathway. Gene traps then are designed to overcome this drawback and so reliably to identify genes underlying the development of phenotypes. It should be pointed out that there are a number of different ‘trapping’ systems, the main difference being the reporter gene construct used. The generic term ‘gene trap’ is therefore used to refer to them collectively. More information on gene traps and their use can be found in the website of the International Gene Trap Consortium (IGTC).
See Conditional knockouts, DNA (deoxyribonucleic acid), Forward genetics, Genotype and phenotype, Mutagens, Reverse genetics, Transgene