Milk protein gene expression of HC11 cells and of mammary glands. RNA of HC11 cells grown with EGF (E) or of differentiated cells (D) and of mouse mammary glands (MGL.) taken at day 12.5 or day 16.5 of pregnancy or at lactation was analyzed by Northern Blot. Upper panel: beta-casein gene expression. Films were exposed either for 3 hours (exp. 3 h) or overnight (exp. o/n). Middle panel: WAP gene expression, exposure was overnight (o/n). Lower panel: photo of the RNA gel to demonstrate amounts and integrity of the blotted RNA.