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 ?
The genomic DNA of tumor and healthy tissues were amplified using coding exon 2 and 3 of c-Myc gene.
WVE-210201 is an investigational stereopure antisense oligonucleotide that has been shown to induce skipping of exon 51 of dystrophin pre-mRNA in nonclinical studies and is intended for the treatment of Duchenne muscular dystrophy.
There are several polymorphic markers in the PAH gene including a Variable Number Tandem Repeat (VNTR), and an intragenic Short Tandem Repeat (STR), which are located 3 kb downstream of the exon 13, and around 200 bp downstream of the exon 3, respectively, in addition to eight Restriction Fragment Length Polymorphisms (RFLP) (Figure 1).
4) The BDNF gene in the rat contains eight 5' noncoding exons (I-IXa), each with a separate promoter and one 3' coding exon (IX) that comprises the entire open reading frame for BDNF protein.
Primer sequences used for amplifying various exon regions of FASN gene
The researchers identified splicing processes that operate only in the stem cells of the worms, and identified numerous alternative exons responsible for stem cell-specific protein variants.
Molecular testing for MET exon 14 skipping should be performed on all lung cancers because this alteration is targetable with currently available therapy, Dr.
Recently in another studies, three SNPs in exon 2 and flanking region and two SNPs in exon 3 and flanking introns in FCGRT gene in buffaloes were observed (18,19).
Thus alternative splicing with exon skipping is a normal feature of MS mRNA in human brain, with different patterns occurring at distinct developmental stages.
The most common mutations affect the juxtamembrane domain encoded by exon 11 (two-thirds of GIST).
Each reported mutation causes skipping of exon 8 at the messenger (mRNA) level, resulting in a frame-shift and produces a prematurely truncated DFNA5 protein.
6] From Gujarat, India, this is the first case reported of BMD with large-scale (>40) exon deletions.