Knockout Animals

Abstract

There are both “conventional” and “conditional” approaches to generating null mice, with the former approach being more common until the application of Cre/LoxP and Flp/FRT systems were developed. Both of these approaches are similar, but conditional methods take advantage of transgenic mice that express recombinase. There are several very good text books describing the construction of null mice, which should be consulted for more in depth coverage of the advantages and disadvantages of this method [11,47]. The overall strategy is depicted in (Figure 3-1). In order to generate a conventional null mouse, a DNA targeting vector must be designed using isogenic genomic DNA. Construction of complex targeting vectors has recently been greatly improved. Since the mouse genome is now sequenced, investigators can identify BAC clones containing the gene of interest without screening a genomic library. Additionally, a recently developed method, termed “recombineering”, allows for rapid construction in less than one month of targeting vectors containing selection cassettes and LoxP/FRT sites [48].