Fig. 4. nlk splice-blocking morpholino inhibits processing of nlk mRNA. Genomic structure of nlk, and RT-PCR analysis of the splicing of intron 5 in the nlk mRNA. Introns are not drawn to scale. Vertical arrow indicates intron/exon boundary between exon 5 and intron 5, targeted by nlk MO. Photo on left shows RT-PCR on RNA isolated from 24-hpf wild-type and nlk MO embryos. The wild-type sample contains only the 233 bp band predicted to result from correct splicing of intron 5. The horizontal arrow indicates the presence of a 320 bp band in the nlk MO sample, which was confirmed by sequencing to be the unspliced product.