A portion of DNA that lies between two exons, is transcribed into RNA, but does not appear in that mRNA after maturation because the i. is removed and the exons spliced together, and so is not expressed (as protein) in protein synthesis. By customary usage, the term is extended to the corresponding regions in the primary transcript of mRNA prior to maturation. SYN: intervening sequence. [inter- + -on]
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in·tron 'in-.trän n a polynucleotide sequence in a nucleic acid that does not code information for protein synthesis and is removed before translation of messenger RNA compare EXON
in·tron·ic in-'trän-ik adj
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in·tron (inґtron) [intervening (sequence) + -on] in eukaryotic genes, a noncoding DNA sequence separating two coding sequences (exons); it is initially transcribed into heterogeneous nuclear RNA (hnRNA) as part of the primary transcript, but is spliced out in the generation of mature messenger RNA (mRNA), prior to translation. By extension, the term also denotes the same sequences in the primary RNA transcript. Called also intervening sequence.Medical dictionary. 2011.