Intron

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An intron is a DNA region within a gene that is not translated into protein. These non-coding sections are transcribed to precursor mRNA (pre-mRNA) and some other RNAs (such as long noncoding RNAs), and subsequently removed by a process called splicing during the processing to mature RNA. After intron splicing (i.e. removal), the mRNA consists only of exon derived sequences, which are translated into a protein.

The word intron is derived from the term intragenic region and also called intervening sequence (IVS)[1]

Contents

Introduction

Introns are common in eukaryotic pre-mRNA, but in prokaryotes they are only found in tRNA and rRNA; introns have variable length and alternate with exons in intron-containing genes.

The number and length of introns varies widely among species, and among genes within the same species. Some eukaryotes, e.g. sac fungi, have evolved genomes with few introns,[2] while the genomes of many other eukaryote groups are rich in introns (several per gene).[3][4]

Alternative splicing of introns within a gene may introduce greater variability of protein sequences translated from a single gene. The control of mRNA splicing is performed by a wide variety of signaling molecules.

Introns may also contain "old code", or sections of a gene that were once translated into a protein, but have since become inactive. It was generally assumed that the sequence of any given intron is junk DNA with no biological function. More recently, however, this is being disputed.[5] For example, a point mutation in intron 7 of the human gene TPH1 is highly correlated to the development of the psychiatric disorder schizophrenia.[6]

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