Figure 4.

Expression patterns of reporter genes in transgenic embryos. Expression of the β-galactosidase gene is detected in the posterior regions of transgenic embryos. The transgenic embryos are staged between days 9.0 and 9.5 of embryonic development. Arrows indicate position of the 14th somite. Enhancer activity of 400-bp mouse (A) and human (B) constructs are shown in the first row. Enhancer activity of 273-bp fin whale (C) and sperm whale (D) constructs are shown in the second row. Enhancer activity of a 400-bp mouse (E) construct carrying the 4-bp deletion of element C is shown in the third row. The structure of mammalian enhancers is described in Fig. 3. f, forelimb; n, neural tube; s, somites.