GENOMIC STRUCTURE OF GROWTH-HORMONE GENES IN CHINOOK SALMON (ONCORHYNCHUS-TSHAWYTSCHA) - PRESENCE OF 2 FUNCTIONAL GENES, GH-I AND GH-II, AND A MALE-SPECIFIC PSEUDOGENE, GH-PSI

Two chinook salmon (Oncorhynchus tshawytscha) growth hormone genes (a functional GH-I gene and a pseudogene, GH-psi) were isolated and chara cterized. The GH-I gene sequence consists of 1.9 kb of 5'-flanking seq uence, 4.1 kb of transcribed region, and 64 bp of 3'-flanking sequence , and contains 6 exons and 5 introns. The pseudogene, GH-psi, spanning 4.1 kb, has a similar structure as the GH-I gene. However, it has one wrong splicing sequence at the intron 1/exon 2 junction, one prematur e termination codon in exon 5, and a deletion in the last half of exon 5 and the first part of intron 5. In addition to GH-I gene and GH-psi , a third GH gene, GH-II, was identified by the polymerase chain react ion (PCR) and subsequently shown to be the second functional GH-II gen e. To study the linkage arrangement of these three GH genes, 50 unrela ted chinook salmon (25 males and 25 females) and one chinook salmon fa mily were analyzed by PCR. The results showed that GH-psi exists only in males and that it segregates from father to sons. These results sug gest that GH-psi is sex specific and probably resides on the Y chromos ome. Together these results indicate that there are three GH genes in the genome of male chinook salmon, and only two GH genes in the female s. The extra GH gene in the male is, however, a pseudogene.