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Within introns, a donor site (5' end of the intron), a branch site (near the 3' end of the intron) and an acceptor site (3' end of the intron) are required for splicing. The splice donor site includes an almost invariant sequence GU at the 5' end of the intron, within a larger, less highly conserved region.
An intron is separated from its exon by means of the splice site. Acceptor-site and donor-site relating to the splice sites signal to the spliceosome where the actual cut should be made. These donor sites, or recognition sites, are essential in the processing of mRNA.
Alternative acceptor site: An alternative 3' splice junction (acceptor site) is used, changing the 5' boundary of the downstream exon. Intron retention : A sequence may be spliced out as an intron or simply retained.
An intron is any nucleotide sequence within a gene that is not expressed or operative in the final RNA product. The word intron is derived from the term intr agenic regi on, i.e., a region inside a gene. [1] The term intron refers to both the DNA sequence within a gene and the corresponding RNA sequence in RNA transcripts. [2]
The outron is an intron-like sequence possessing similar characteristics such as the G+C content [3] and a splice acceptor site that is the signal for trans-splicing. [4] [5] Such a trans-splice site is essentially defined as an acceptor (3') splice site without an upstream donor (5') splice site.
A splice donor site being joined to a splice acceptor site further upstream in the primary transcript, yielding a circular transcript. [8] The notion that circularized transcripts are byproducts from imperfect splicing is supported by the low abundance and the lack of sequence conservation of most circRNAs, [9] but has been challenged. [8] [10] [3]
U2 snRNA is implicated in intron recognition through a 7-12 nucleotide sequence between 18-40 nucleotides upstream of the 3ยด splice site known as the branch point sequence (BPS). [1] [2] In yeast, the consensus BPS is 7 nucleotide residues in length and the complementary recognition sequence within the U2 snRNA is 6 nucleotides.
Method. Trapping is performed with gene trap vectors whose principal element is a gene trapping cassette consisting of a promoterless reporter gene and/or selectable genetic marker, flanked by an upstream 3' splice site (splice acceptor; SA) and a downstream transcriptional termination sequence (polyadenylation sequence; polyA). When inserted ...