Figure 6

Distribution of Delta nascent transcripts in an early stage 3 embryo. An embryo at the onset of morphological segmentation hybridized with a Delta probe containing mostly intron sequences. This probe detects unprocessed nascent transcripts much more strongly than spliced cytoplasmic transcripts. At this early stage there are prominent nuclear dots of nascent transcript in many cells of the peri-proctodeal region (insert A3); double nuclear dots are often visible (magenta arrows), showing transcription associated with both copies of the gene. In more mature Delta stripes, transcript is still present at high levels in the cytoplasm, but nuclear dots are less frequent and less prominent (insert A2). (This embryo is slightly younger than that shown in Figure 2A. Only the mandibular segment was morphologically distinct (position marked by black arrowhead). Note that embryos at this stage extend around much of the egg, and are, therefore, distorted and split at the lateral margins when flattened. A forming head is on the left. Asterisk marks the proctodeum. Part of the head is missing. Scale bar in A: 200 μm, in B: 50 μm, in C: 20 μm.