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Table 4 Summary of the types of exons present in each of the genomes and their functions

From: The Sequence Ontology: a tool for the unification of genome annotations

  Exon part of gene with single transcript Exon part of one transcript of alternatively spliced gene (UNIQUE) Exon part of fraction of alternatively spliced transcripts (SOMETIMES_FOUND) Exon part of all of the transcripts of alternatively spliced gene (ALWAYS_FOUND)
Percentage of all exons 60.1% 16.1% 5.2% 18.6%
Coding 94.5% 68% 73% 93%
Non-coding 4.5% 32% 19% 3.5%
Coding/non-coding - - 8% 3.5%
  1. Exons of alternatively spliced genes were divided into three categories based on the binary product and difference operations. UNIQUE exons (column 2) occur in only a single transcript; SOMETIMES_FOUND exons (column 3) occur in some, but not all of a gene's alternatively spliced transcripts. ALWAYS_FOUND exons occur in every alternative transcript. The table rows show the breakdown of each exon class with respect to function, i.e., coding exons are those that consist at least partially of translated nucleotides, whereas non-coding exons consist entirely of UTR sequence. In some genes, an exon may be coding in one transcript and non-coding in another, depending on the annotated start and stop codons and the phase of the upstream intron; these exons are denoted as coding/non-coding exons. For reference purposes, the breakdown of exons in single-transcript genes is shown in column 1.