Contents

09 July 1993
Vol 261, Issue 5118

About The Cover

Mouse embryo at 11.5 days of development. This embryo harbors a -galactosidase transgene linked to the promoter of the myogenin gene, active in skeletal muscle formation. The expression pattern of the transgene (in blue) reflects that of the endogenous myogenin locus and is restricted to the myotomal region of the somites and the limb buds. Mutations in the myogenin promoter suggest that separable regulatory elements govern myogenin expression in somites and limb buds. See page 215. [Photograph: Tse-Chang Cheng]