Evolution of a complex eukaryotic gene.

Our current efforts to understand the evolutionary origin of the ovomucoid gene are reviewed. Sequence analyses have suggested that introns were present in the primordial ovomucoid gene before birds and mammals diverged, about 300 million years ago. Our work suggests that the present ovomucoid gene has evolved from primordial ovomucoid gene by two separate intragenic duplications followed by the addition of a final segment which codes for a secretory signal sequence. The 3 domains of the secreted peptide and also the signal sequence are constructed by an apparent assembly of exons which code for individual peptide segments. The exact position of introns within the ovomucoid gene has been defined and the results support the theory that introns separate gene segments that code for functional domains of proteins and provide insight into the manner by which eukaryotic genes were constructed during the process of evolution.