text: The split gene theory implies that structural features of split genes predicted from computer-simulated random sequences occur in eukaryotic split genes. This is borne out in most known split genes. The sequences exhibit a nearly perfect negative exponential distribution of ORF lengths. With rare exceptions, eukaryotic gene exons fall within the predicted 600 base maximum.
  The theory correctly predicts that exons are delimited by stop codons, especially at the 3’ ends of exons. Actually they are precisely delimited more strongly at the 3’ ends of exons and less strongly at the 5’ ends in most known genes, as predicted. These stop codons are the most important functional parts of both splice junctions. The theory thus provides an explanation for the “conserved” splice junctions at the ends of exons and for the loss of these stop codons along with introns when they are spliced out. The theory correctly predicts that splice junctions are randomly distributed in eukaryotic DNA sequences. The theory correctly predicts that splice junctions present in transfer RNA genes and ribosomal RNA genes,  do not contain stop codons. The lariat signal, another sequence involved in the splicing process, also contains stop codons.
  The theory correctly predicts that introns are non-coding and that they are mostly non-functional. Except for some intron sequences including the donor and acceptor splice signal sequences and branch point sequences, and possibly the intron splice enhancers that occur at the ends of introns, which aid in the removal of introns, the vast majority of introns are devoid of any functions. The theory does not exclude rare sequences within introns that could be used by the genome and the cell, especially because introns are so long.
  Thus, the theory's predictions are precisely corroborated by the major elements in modern eukaryotic genomes.
  Comparative analysis of the modern genome data from several living organisms found that the characteristics of split genes trace back to the earliest organisms. These organisms could have contained the split genes and complex proteins that occur in today's living organisms.
  Studies employing maximum likelihood analysis found that the earliest eukaryotic organisms contained the same genes as modern organisms with yet a higher intron density. Comparative genomics of many organisms including basal eukaryotes (considered to be primitive eukaryotic organisms such as Amoeboflagellata, Diplomonadida, and Parabasalia) showed that intron-rich split genes accompanied and spliceosome from modern organisms were present in their earliest forebears, and that the earliest organisms came with all the eukaryotic cellular components.