Figure 3.

Southern blot analysis demonstrating loss of the I-SceI site and duplication of the Rb locus. Lanes are marked with W (for wild-type) if alleles are unaltered in copy number and D if an allele is duplicated. The neo gene probe is as in Fig. 2. (A) Analysis of genomic DNA cleaved with BglII/I-SceI from KL neo⁺ clones. Restriction fragment sizes are indicated for each of the alleles, with both the parental and neo⁺ alleles shown for K (K-Sneo and K-neo+, respectively). The KL clone in lane De has a deletion in the recombinant L–K allele (clone C6; see text). (B) Analysis of genomic DNA cleaved with BglII/I-SceI from MN neo⁺ clones. Restriction fragment sizes are indicated for each of the alleles, with both the parental and neo⁺ allele shown for M (M-Sneo and M-neo+, respectively). All MN clones in lanes labeled D have duplicated N alleles, except one clone that has an additional parental M-Sneo allele, as indicated.