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FIG. 5. Injection of blastomere C3 with Lac Z mRNA results in
variable labeling. Embryos injected solely with Lac Z mRNA into
blastomere C3 at st. 6 were cultured to st. 32, stained for Lac Z
activity (red), and probed by in situ hybridization for globin expression
(turquoise). (A, C, D) The range of results observed. While globin
expression is constant from embryo to embryo, Lac Z activity is
variable and sometimes overlaps with globin expression in the VBI
(A–C). Although Lac Z detected somites in all C3-injected embryos, in
some specimens (A, C), it labeled both the dorsal (DS) and ventral (VS)
aspect of the somites, while in others (D), it labeled the dorsal, but not
the ventral aspect. Other tissues showing variable Lac Z expression
include the pronephros (P), the lateral plate (LP), and the branchial
arches (BA), all tissues identified in previous maps as normal descendants
of C3 (Dale and Slack, 1987; Moody, 1987). These results
suggest that Lac Z mRNA does not diffuse well and generally labels
only subsets of C3 progeny. |
