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RNA splicing. RNA splicing is a process in molecular biology where a newly-made precursor messenger RNA (pre- mRNA) transcript is transformed into a mature messenger RNA (mRNA). It works by removing all the introns (non-coding regions of RNA) and splicing back together exons (coding regions). For nuclear-encoded genes, splicing occurs in the ...
Simple illustration of an unspliced mRNA precursor, with two introns and three exons (top). After the introns have been removed via splicing, the mature mRNA sequence is ready for translation (bottom). A particularly extreme case is the Drosophila dhc7 gene containing a ≥3.6 megabase (Mb) intron, which takes roughly three days to transcribe.
Alternative splicing produces three protein isoforms. Protein A includes all of the exons, whereas Proteins B and C result from exon skipping. Alternative splicing, or alternative RNA splicing, or differential splicing, is an alternative splicing process during gene expression that allows a single gene to produce different splice variants.
The term exon refers to both the DNA sequence within a gene and to the corresponding sequence in RNA transcripts. In RNA splicing, introns are removed and exons are covalently joined to one another as part of generating the mature RNA. Just as the entire set of genes for a species constitutes the genome, the entire set of exons constitutes the ...
Alternative splicing of the primary transcript. The effect of alternative splicing in gene expression can be seen in complex eukaryotes which have a fixed number of genes in their genome yet produce much larger numbers of different gene products. [9] Most eukaryotic pre-mRNA transcripts contain multiple introns and exons.
The majority of eukaryotic pre-mRNAs consist of alternating segments called exons and introns. [10] During the process of splicing, an RNA-protein catalytical complex known as spliceosome catalyzes two transesterification reactions, which remove an intron and release it in form of lariat structure, and then splice neighbouring exons together. [11]
There are multiple alternative splicing modes: exon skipping (most common splicing mode in humans and higher eukaryotes), mutually exclusive exons, alternative donor or acceptor sites, intron retention (most common splicing mode in plants, fungi, and protozoa), alternative transcription start site (promoter), and alternative polyadenylation. [118]
Pre-mRNA has both introns and exons. As a part of the maturation process, RNA splicing removes the non-coding RNA introns leaving behind the exons, which are then spliced and joined together to form the mature mRNA. [3] [8] Splicing is conducted by the spliceosome. The spliceosome is a large ribonucleoprotein which cleaves the RNA at the ...