FIG. 7.

In situ hybridization with a downstream probe complementary to the 3′ untranscribed region of histone H3 mRNA to detect misprocessed H3 mRNA in vivo. The sequence used to generate the antisense H3-ds probe for use in detecting only misprocessed forms of histone H3 is shown by brackets in Fig. 5D. Each panel shows a whole embryo oriented as in Fig. 6 that was hybridized with the H3-ds probe (A to D, F, and H) or a coding region H3 probe. (E and G). The embryos stained with the H3-ds probe are siblings collected from heterozygous dSLBP¹⁵/+ parents and provide examples of the three different phenotypic classes observed. (A) Stage 12 +/+. Most cells are beginning to enter cell cycle 17 at this time. (B) Stage 12 dSLBP¹⁵/+; (C) stage 13 +/+; (D) stage 13 dSLBP¹⁵/+; (E) stage 12 yw⁶⁷ wild type; (F) stage 12 dSLBP¹⁵/dSLBP¹⁵; (G) stage 14 yw⁶⁷ wild type; (H) stage 14 dSLBP¹⁵/dSLBP¹⁵. Persistence of misprocessed histone H3 message is observed in nonreplicating cells of the pharanx, anterior midgut, hindgut, and anal pads (indicated from left to right, respectively, by arrows in H and G).