title: The ovalbumin gene family: structure of the X gene and evolution of duplicated split genes.
abstract: The X, Y and ovalbumin genes, which are found within a 40 kb region of the chicken genome, are all expressed in oviduct under steroid hormone control, and share some sequence homologies. We have now cloned the complete X gene and have analyzed its structure. It codes for two RNA species, X and X'; both are coded by eight exons and appear to differ only by the size of their 3' untranslated region, X' RNA being 1400 nucleotides longer than X RNA. The striking similarity in the number and length of the exons which constitute the X, Y or ovalbumin genes establishes that they have evolved from a common ancestor gene by duplication events. Comparison of selected regions of the X and ovalbumin genes indicates that the exon sequences coding for protein and the location of the splice junctions have been well-conserved. The introns and the 3' untranslated exonic sequences have diverged much more rapidly. Four regions of apparently unrelated repetitive sequences are found both outside the X gene and within it (in two introns and in the sequence coding for the 3' untranslated part of X'RNA). The intragenic repetitive sequences have no counterpart in the ovalbumin and Y genes.
mesh_terms: D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D002645:Chickens; D004247:DNA / Q000235:genetics; D005784:Gene Amplification; D005796:Genes; D009694:Nucleic Acid Precursors / Q000235:genetics; D010047:Ovalbumin / Q000235:genetics*; D012332:RNA, Heterogeneous Nuclear / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics
chemical_list: D009694:Nucleic Acid Precursors; D012332:RNA, Heterogeneous Nuclear; D012333:RNA, Messenger; D010047:Ovalbumin; D004247:DNA