FIG. 1.

Structure and evolution of type II CGβ genes. (A) Diagram of the LH/CGβ gene cluster on human chromosome 19q13.33. Straight arrows indicate direction of transcription, the large curved arrow denotes inverted segmental duplication of the original CGβ1 gene, and arrowheads depict snaR-G genes. (B) Schematic of LHβ and type I and II CGβ gene structures, illustrating the replacement in type II CGβ genes of a segment common to type I CGβ genes with an insert containing snaR-G (dotted lines). Untranslated regions (UTRs) are depicted as solid boxes; open reading frames (ORFs) are shown as open boxes; introns and promoter regions are shown by solid lines; directions of transcription are shown by bent arrows. The CGβ1/2 first exon is defined here by the first donor splice site (6), and its UTRs (gray boxes) are defined by the first potential ORF. (Adapted from reference 25a with permission of the publisher.)