Abstract
We describe the cloning, characterisation and chromosomal mapping of the chicken hprt gene together with the construction of two counter selectable hprt-/- DT40 derived cell lines. One of these cell lines contains a stably integrated gene encoding a conditionally active cre recombinase and thus allows efficient manipulation of targeted loci by site-specific recombination. These cell lines will enhance the utility of the hyper-recombinogenic DT40 cell line as a system for the genetic analysis of cell autonomous functions in vertebrates and as a tool for mammalian chromosome engineering.