The Xenopus tropicalis periostin C-terminal region in the UCSC genome browser. (A) The 'Spliced EST' track shows a cluster of eight additional genomic copies of exon 19 (referred to here as exons 19A - 19H) immediately downstream of exon 19. These exons, not represented in the RefSeq record, are subject to alternative splicing in various combinations. The asterisk (*) marks a region where multiple ESTs have subsequences unaligned to genomic sequence due to a gap in the assembly (not shown), which we resolved to be exon 21 (see main text). (B) Amino acid sequences of exons 19 and 19A - 19H. The very high degree of similarity among these is evident.