Biochemistry, molecular genetics, and biology glossary terms for Companion Sites.


Splice-sites are the intron-exon junctions in the precursor mRNA of eukaryotes, and are recognized by trans-acting factors (prokaryotic RNAs are mostly polycistronic).

In constitutive nuclear pre-mRNA splicing the intronic sequences are excised and the exons are ligated to generate the mature, spliced mRNA.

Pre-mRNA splicing is a form of RNA processing, which yields a mature mRNA comprising the coding exons that direct sequencing of amino acids inserted into elongating polypeptides during cytoplasmic translation at ribosomes. However, a cell typically splices a single mRNA transcript in multiple ways to generate an assortment of proteins. Alternatively spliced introns tend to lie between those exonal segments of a gene that encode the functional units, or domains, of a protein (ORF).

The length and sequence of nucleotides in nuclear pre-mRNA introns is highly variable, except for the short conserved sequences at the 5´ and 3´ splice sites and the branch points. These splice sites immediately surrounding the intron-exon junction can be regarded as consensus sequences.

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