exon
ex·on
E0279300 (ĕk′sŏn)exon
(ˈɛksɒn)exon
(ˈɛksɒn)ex•on
(ˈɛk sɒn)n.
| Noun | 1. | exon - sequence of a gene's DNA that transcribes into protein structures; "exons are interspersed with introns" |
| 单词 | exon | |||
| 释义 | exonex·onE0279300 (ĕk′sŏn)exon(ˈɛksɒn)exon(ˈɛksɒn)ex•on(ˈɛk sɒn)n.
exonExonIn 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]exonex·on(ek'son),exon(ĕk′sŏn)ex·on(ek'son)exonThe segment of deoxyribonucleic acid (DNA) in a gene that codes for some part of the messenger ribonucleic acid (RNA). Any segment that is represented in the RNA product. Segments that do not code for RNA are called introns.exonorextron(‘ex'for expressed) or - the DNA segments of an INTERRUPTED split gene that are transcribed into RNA and then into the gene product. Exons occur along the length of the gene, and are separated by segments called INTRONS whose sequences are also transcribed into RNA. The intron RNA segments are then excised, leaving behind the exon RNA segments that join up to form a functional RNA molecule, a process called RNA SPLICING.exon
Synonyms for exon
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