Figure 3.

Several novel exons can be found in the gene SHH, which encodes a human homolog of Sonic hedgehog. The 5′-RACE/array profiling was performed with primers designed in exons 2 and 3 of the annotated form. The 3′-RACE/array profiling was performed with primers positioned in two unannotated transfrags in intron 1 (indicated by the arrows). A significant amount of signal can be seen in intron 1 of the gene, representing alternative exons of this gene. The annotated form of exon 3 appears to be represented as two different exons. An alternative 3′-exon was detected downstream of the annotated gene bounds. The maps of cloned RT-PCR products representing different alternative isoforms of transcripts containing novel exons are shown at the bottom.