Non-coding mRNA is a kind of newly discovered mRNA. Though spliced and tailed,it does not have any typical ORF. Up to date, several such genes have been cloned: H19 gene, XIST gene, XLSIRT gene, His-1 gene, bic gene, rox1 and rox2 genes. Non-coding mRNA play important roles in the development of embryos, in the inactivation of X chromosome and in the tumorigenesis.