Genomic organization of rat prolactin and growth hormone genes.

Five overlapping cloned DNAs containing the rat prolactin gene and its flanking sequences, as well as one cloned DNA containing the rat growth hormone gene and its flanking sequences, were isolated from a chromosomal DNA library. They were characterized by restriction enzyme mapping and electron microscopy. In each gene, the structural gene sequence coding for mature mRNA of a length of about 1 kilobase is split into at least five segments by a minimum of four intervening sequences. The two genes are similar in the length and organization of their coding regions, consistent with the suggestion that they are derived from a common ancestral gene. However, the two genes differ greatly in the lengths of their intervening sequences. That leads to a total gene length of 10 kilobase pairs for the prolactin and 2.1 kilobase pairs for the growth hormone gene. At least one intervening sequence appears to be in the 5' nontranslated regions of the prolactin and growth hormone mRNA coding sequences.