Fig. 1.

Gene targeting and analysis of ES cells and mice. (A) Strategy for knocking in a human rhodopsin-GFP fusion gene in place of the mouse rhodopsin gene. The mouse rhodopsin locus is shown in black, with exons and polyadenylation sites indicated by small rectangles and stars, respectively. The HPRT minigene (gray) is driven by the phosphoglycerate kinase (PGK) promoter. The human rhodopsin-GFP fusion gene is shown in white, with the GFP portion crosshatched. Small arrows show the points of fusion between the mouse sequences and the HPRT or human rhodopsin sequences. White inverted triangles indicate locations of lox sites. P/H refers to two different constructs: one construct carrying an upstream LoxP site and the other construct carrying an upstream LoxH site. HR, homologous recombination; SR, segmental replacement. (B) Southern-blot analysis of ES cells and germline mice. Restriction enzymes used to digest genomic DNA are given in parentheses, and fragment sizes are given in kilobases. Both 5′- and 3′-specific probes were used to verify the structure of the modified locus. (C) PCR analysis of tail DNA from mice. PCR product sizes are indicated in kilobases.