exon

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Exon

In split genes, a portion that is included in the ribonucleic acid (RNA) transcript of a gene and survives processing of the RNA in the cell nucleus to become part of a spliced messenger RNA (mRNA) or structural RNA in the cell cytoplasm. Split genes are those in which regions that are represented in mature mRNAs or structural RNAs (exons) are separated by regions that are transcribed along with exons in the primary RNA products of genes, but are removed from within the primary RNA molecule during RNA processing steps (introns). See Intron, Ribonucleic acid (RNA)

Exons comprise three distinct regions of a protein-coding gene. The first is a portion that is not translated into protein, but contains the signal for the beginning of RNA synthesis, and sequences that direct the mRNA to ribosomes for protein synthesis. The second is a set of exons containing information that is translated into the amino acid sequence of a protein. The third region of a gene that becomes part of an mRNA is an untranslated end portion that contains signals for transcription termination and for the addition of a polyadenylate tract at the end of a transcript.

The mechanism by which the exons are joined in RNA copies of genes is called RNA splicing, and it is part of the maturation of mRNAs and some transfer and ribosomal RNAs (tRNAs and rRNAs) from primary transcripts of genes. Three different RNA splicing processes have been identified. One involves mRNA precursors in nuclei, and specific sequences at exon-intron junctions that are recognized by certain nuclear ribonucleoprotein particles that facilitate the cleavage and ligation of RNA. Another applies to nuclear precursors of tRNA, where splice sites are determined by structural features of the folded RNA molecules. The third form of splicing was discovered in studies of protozoan rRNA synthesis, and has also been shown to be a part of the maturation of both rRNA and mRNA in yeast mitochondria; it is an autocatalytic process that requires neither an enzyme nor added energy such as from adenosine triphosphate. See Gene, Genetic code, Protein, Ribosomes

exon

[′ek‚sän]
(genetics)
The segment or segments of a gene which code for its final messenger ribonucleic acid.
References in periodicals archive ?
Synonymous and non-synonymous changes in exonic region
Exonic nucleotide variants and linkage disequilibrium (LD) block of the glutamate receptor-interacting protein 1 (GRIP1) gene (Exon 20 and 25).
It should also be noted that the variant is found at the first nucleotide of exon 5, and is, therefore, the only missense exonic splice variant to have been identified.
We identified nine SNPs covering exonic and intronic regions of the [beta]2M gene in murrah breed of buffaloes.
In this a two-stage approach is used; designing of a set of two identifier to identify exonic region margins is collected with a worldwide exemplary of gene configuration.
The silent mutation may cause exon 7 skipping by disrupting an exonic splicing enhancer, as proposed by Kuehl et al.
It was reported that the integration of gene cassette using [phi] C31 integrase is specific and probably carried out in exonic locations 25.
Primers were designed to amplify eight segments between 200 and 400 pb (table 1) of the exonic and intronic regions adjacent to Shh exons.
N-acetylgalactosamine-6-sulfate sulfatase exonic point mutations in classical Morquio and mild cases.
578_579 + 5delAAGTATG [710_711 + 5del7] deletion that spans an exonic splice site causes a frameshift and could affect splicing at the same time.
2002) Disruption of an SF2/ASF-dependent exonic splicing enhancer in SMN2 causes spinal muscular atrophy in the absence of SMN 1.