The difference between them is that HCA90 contains a 108 bp additional exon, which belongs to Alu repeat sequences and is inserted between exon 10 and 11 of the HCA519 gene.

• 其中HCA90所特有的外显子序列长 10 8bp ；属Alu重复序列片段 ；插入于HCA5 19外显子 10和 11之间 ；原为HCA5 19内含子序列 .