Primary structure and evolution of rat growth hormone gene

Area of Science:

• Molecular Biology
• Genetics
• Evolutionary Biology

Background:

• The rat growth hormone (rGH) gene plays a crucial role in mammalian growth and metabolism.
• Understanding gene structure is key to deciphering gene function and evolutionary relationships.

Purpose of the Study:

• To isolate and characterize the complete rat growth hormone gene, including its flanking regions.
• To analyze the structural organization, including introns and exons, of the rGH gene.
• To explore potential evolutionary links between growth hormone, prolactin, and placental lactogen genes.

Main Methods:

• Isolation of the rGH gene using bacteriophage cloning from a rat chromosomal DNA library.
• Identification of the structural gene sequence via hybridization with rat growth hormone cDNA.
• Determination of the complete DNA sequence of the gene and flanking regions.

Main Results:

• The rat growth hormone gene was isolated as an 11.4-kilobase DNA fragment.
• The structural gene is approximately 2.1 kilobases and contains four intervening sequences (introns).
• A dispersed repetitive DNA sequence was identified within the largest intron, flanked by direct repeats.

Conclusions:

• The mosaic structure of the rGH gene, with its exons and introns, may relate to the diverse biological activities of growth hormone.
• The gene's structure provides insights into its evolution from ancestral genes, potentially related to prolactin and placental lactogen.
• Mobile repetitive DNA elements within introns might influence gene size variation and genomic rearrangements.