Figure 1.

Gene targeting in mice. (A) The targeting construct of the mouse Parp and predicted structure of the targeted Parp locus. The targeting vector contains a 1.1-kb pMC1-neo^r-poly(A) cassette inserted in the 6-kb fragment of an AccI–XhoI Parp genomic fragment and a 0.8-kb DT-A fragment at the 3′ terminus. In the targeted allele, the reversely oriented pMC1-neo^r-poly(A) cassette was inserted into AatI site in exon 1, 10 bases downstream of the first ATG. The length of diagnostic fragments and probes for Southern blot analysis are shown. The targeted allele yielded a 5.7-kb band, and the intact allele yielded a 4.5- or 4.8-kb band, the result of the polymorphism between ICR and 129SvJ. The hatched box represents Parp exon 1. The restriction enzyme sites are shown: Aa, AatI; Ac, AccI; HIII, HindIII; K, KpnI; Xh, XhoI; Xb, XbaI. (B) Southern blot analysis of genomic DNA from offspring derived from Parp^+/− mice intercrosses. A representative result is shown. Genomic DNA was isolated from a tail biopsy and digested with HindIII and XbaI, and hybridization was carried out with the 3′ probe (0.5 kb of XhoI–HindIII fragment as shown in A). The 5.7-kb fragment indicates a homologous recombinant allele. Genomic DNAs from J1 and clone 205 ES cells, ICR mice were prepared and used for Southern blot analysis in parallel.