Four major applications of transposon technology in vertebrate functional genomics. The four organisms surrounding the DNA transposon indicate that certain transposons, such as elements belonging to the mariner family, can be used in a broad range of hosts as their movement is largely independent of host functions. (a) Most transposons can disrupt host genes upon insertion. Such insertions can be somatic insertions, which can be used to discover and analyze cancer genes, or germline insertions resulting in heritable mutations that produce phenotypic change in the progeny. (b) Transposons can also be used to deliver exogenous genes into the organism through somatic cell transgenesis (in gene therapy) or germline transgenesis (producing transgenic animals at high efficiency).