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 ?
A number of promoter, exonic and intronic polymorphisms in the ER-[beta] gene have been identified, showing their direct biological significance and association with human diseases.
It is also predominantly deduced that most of heterozygous variants are observed in intronic regions rather than exonic part of the gene.
In multiplex PCR group, one male fetus was identified as a patient with gene exonic deletion.
A1 B1 C1 A12 B12 C12 Exonic 94.02% 95.22% 94.44% 95.16% 94.21% 94.69% Intergenic 1.92% 1.64% 1.78% 1.64% 1.79% 1.71% Intronic 4.06% 3.14% 3.78% 3.20% 4.00% 3.60% Note: Table made from pie chart.
With specific focus on exonic regions of the genes and nonsynonymous mutations, "R" analysis demonstrated two genes that were within acceptable ExAC allele frequency and CADD score range (<0.01, >10): GPAA1 and RECQL4, suggestive of significant interaction with SLC39A4 in developing the disease phenotype in B03.
[25] "PESX: Putative Exonic Splicing enhancers/Silencers," https:// omictools.com/putative-exonic-splicing-enhancers-silencerstool.
Accumulating evidence of the LUZP2 role in the genetic component of a spectrum of neurocognitive phenotypes, based on genome-wide association with AD, schizophrenia, cognitive, and memory functions [11-17], as well as on the findings of exonic variants shared among the affected siblings with a familial variant of Alzheimer's disease with neuroimaging features of Alzheimer's disease but lacking amyloid-b deposits in the brain [47], suggests its functional implication in the neurodegeneration and impaired cognition in humans.
At least 9 single nucleotide polymorphisms (SNP's) have been known in the exonic gene region23.
An analysis of FAM190A's exonic sequences has identified a single coiled coil domain spanning Exons 8-9 and a serine-rich domain involving Exon 2, but it is not clear how these domains effect FAM190A function.
A total 15 polymorphisms; 12 in intronic and 3 in exonic region, were identified.
fimicola, a total of 245 base substitutions were observed in the exonic region of laccase gene.
The exonic DNA library was then sequenced on the Illumina HiSeq2000 platform.