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Trans-splicing
''Trans''-splicing is a special form of RNA processing where exons from two different primary RNA transcripts are joined end to end and ligated. It is usually found in eukaryotes and mediated by the spliceosome, although some bacteria and archaea also have "half-genes" for tRNAs. Genic ''trans''-splicing Whereas "normal" (''cis''-)splicing processes a single molecule, ''trans''-splicing generates a single RNA transcript from multiple separate pre-mRNAs. This phenomenon can be exploited for molecular therapy to address mutated gene products. Genic trans-splicing allows variability in RNA diversity and increases proteome complexity. Oncogenesis While some fusion transcripts occur via ''trans''-splicing in normal human cells, ''trans''-splicing can also be the mechanism behind certain oncogenic fusion transcripts. SL ''trans''-splicing Spliced leader (SL) ''trans''-splicing is used by certain microorganisms, notably protists of the Kinetoplastae class to express genes. I ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RNA Splicing
RNA splicing is a process in molecular biology where a newly-made precursor messenger RNA (pre-mRNA) transcription (biology), transcript is transformed into a mature messenger RNA (Messenger RNA, mRNA). It works by removing all the introns (non-coding regions of RNA) and ''splicing'' back together exons (coding regions). For nuclear genes, nuclear-encoded genes, splicing occurs in the cell nucleus, nucleus either during or immediately after Transcription (biology), transcription. For those eukaryotic transcription, eukaryotic genes that contain introns, splicing is usually needed to create an mRNA molecule that can be translation (biology), translated into protein. For many eukaryotic introns, splicing occurs in a series of reactions which are catalyzed by the spliceosome, a complex of small nuclear ribonucleoproteins (snRNPs). There exist self-splicing introns, that is, ribozymes that can catalyze their own excision from their parent RNA molecule. The process of transcription, spli ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Splicing (genetics)
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 nucleus either during or immediately after transcription. For those eukaryotic genes that contain introns, splicing is usually needed to create an mRNA molecule that can be translated into protein. For many eukaryotic introns, splicing occurs in a series of reactions which are catalyzed by the spliceosome, a complex of small nuclear ribonucleoproteins ( snRNPs). There exist self-splicing introns, that is, ribozymes that can catalyze their own excision from their parent RNA molecule. The process of transcription, splicing and translation is called gene expression, the central dogma of molecular biology. Splicing pathways Several methods of RNA spli ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chimera (EST)
In molecular biology, and more importantly high-throughput DNA sequencing, a chimera is a single DNA sequence originating when multiple transcripts or DNA sequences get joined. It can occur in various contexts. Chimeric reads are generally considered artifacts in sequencing applications (such aamplicon sequencing and are filtered out from the data during processing to prevent spurious inferences of biological variation. In a different context, the deliberate creation of artificial chimeras can also be a useful tool in the molecular biology. For example, in protein engineering, "chimeragenesis (forming chimeras between proteins that are encoded by homologous cDNAs)" p. 424 is one of the "two major techniques used to manipulate cDNA sequences". For gene fusions that occur through natural processes, see chimeric genes and fusion genes. Description Transcript chimera A chimera can occur as a single cDNA sequence originating from two transcripts. It is usually considere ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pre-mRNA
A primary transcript is the single-stranded ribonucleic acid ( RNA) product synthesized by transcription of DNA, and processed to yield various mature RNA products such as mRNAs, tRNAs, and rRNAs. The primary transcripts designated to be mRNAs are modified in preparation for translation. For example, a precursor mRNA (pre-mRNA) is a type of primary transcript that becomes a messenger RNA (mRNA) after processing. Pre-mRNA is synthesized from a DNA template in the cell nucleus by transcription. Pre-mRNA comprises the bulk of heterogeneous nuclear RNA (hnRNA). Once pre-mRNA has been completely processed, it is termed "mature messenger RNA", or simply "messenger RNA". The term hnRNA is often used as a synonym for pre-mRNA, although, in the strict sense, hnRNA may include nuclear RNA transcripts that do not end up as cytoplasmic mRNA. There are several steps contributing to the production of primary transcripts. All these steps involve a series of interactions to initiate and co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ctenophores
Ctenophora (; ctenophore ; ) comprise a phylum of marine invertebrates, commonly known as comb jellies, that inhabit sea waters worldwide. They are notable for the groups of cilia they use for swimming (commonly referred to as "combs"), and they are the largest animals to swim with the help of cilia. Depending on the species, adult ctenophores range from a few millimeters to in size. Only 100 to 150 species have been validated, and possibly another 25 have not been fully described and named. The textbook examples are cydippids with egg-shaped bodies and a pair of retractable tentacles fringed with tentilla ("little tentacles") that are covered with colloblasts, sticky cells that capture prey. Their bodies consist of a mass of jelly, with a layer two cells thick on the outside, and another lining the internal cavity. The phylum has a wide range of body forms, including the egg-shaped cydippids with retractable tentacles that capture prey, the flat generally combless pla ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Open Reading Frames
In molecular biology, open reading frames (ORFs) are defined as spans of DNA sequence between the start and stop codons. Usually, this is considered within a studied region of a prokaryotic DNA sequence, where only one of the six possible reading frames will be "open" (the "reading", however, refers to the RNA produced by transcription of the DNA and its subsequent interaction with the ribosome in translation). Such an ORF may contain a start codon (usually AUG in terms of RNA) and by definition cannot extend beyond a stop codon (usually UAA, UAG or UGA in RNA). That start codon (not necessarily the first) indicates where translation may start. The transcription termination site is located after the ORF, beyond the translation stop codon. If transcription were to cease before the stop codon, an incomplete protein would be made during translation. In eukaryotic genes with multiple exons, introns are removed and exons are then joined together after transcription to yield the fi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Outron
An outron is a nucleotide sequence at the 5' end of the primary transcript of a gene that is removed by a special form of RNA splicing during maturation of the final RNA product. Whereas intron sequences are located inside the gene, outron sequences lie outside the gene. Characteristics The outron is an intron-like sequence possessing similar characteristics such as the G+C content and a splice acceptor site that is the signal for ''trans''-splicing. Such a ''trans''-splice site is essentially defined as an acceptor (3') splice site without an upstream donor (5') splice site. In eukaryotes such as euglenozoans, dinoflagellates, sponges, nematodes, cnidarians, ctenophores, flatworms, crustaceans, chaetognaths, rotifers, and tunicates, the length of spliced leader (SL) outrons range from 30 to 102 nucleotides (nt), with the SL exon length ranging from 16 to 51 nt, and the full SL RNA length ranging from 46 to 141 nt. Processing In standard cis-splicing, the donor s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Operon
In genetics, an operon is a functioning unit of DNA containing a cluster of genes under the control of a single promoter. The genes are transcribed together into an mRNA strand and either translated together in the cytoplasm, or undergo splicing to create monocistronic mRNAs that are translated separately, i.e. several strands of mRNA that each encode a single gene product. The result of this is that the genes contained in the operon are either expressed together or not at all. Several genes must be ''co-transcribed'' to define an operon. Originally, operons were thought to exist solely in prokaryotes (which includes organelles like plastids that are derived from bacteria), but since the discovery of the first operons in eukaryotes in the early 1990s, more evidence has arisen to suggest they are more common than previously assumed. In general, expression of prokaryotic operons leads to the generation of polycistronic mRNAs, while eukaryotic operons lead to monocistronic mRNAs ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polycistronic
A cistron is an alternative term for "gene". The word cistron is used to emphasize that genes exhibit a specific behavior in a cis-trans test; distinct positions (or loci) within a genome are cistronic. History The words ''cistron'' and ''gene'' were coined before the advancing state of biology made it clear that the concepts they refer to are practically equivalent. The same historical naming practices are responsible for many of the synonyms in the life sciences. The term cistron was coined by Seymour Benzer in an article entitled ''The elementary units of heredity''. also reprinted in The cistron was defined by an operational test applicable to most organisms that is sometimes referred to as a cis-trans test, but more often as a complementation test. Definition For example, suppose a mutation at a chromosome position x is responsible for a change in recessive trait in a diploid organism (where chromosomes come in pairs). We say that the mutation is recessive because t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ciona Intestinalis
''Ciona intestinalis'' (sometimes known by the common name of vase tunicate) is an ascidian (sea squirt), a tunicate with very soft tunic. Its Latin name literally means "pillar of intestines", referring to the fact that its body is a soft, translucent column-like structure, resembling a mass of intestines sprouting from a rock. It is a globally distributed cosmopolitan species. Since Linnaeus described the species, ''Ciona intestinalis'' has been used as a model invertebrate chordate in developmental biology and genomics. Studies conducted between 2005 and 2010 have shown that there are at least two, possibly four, sister species. More recently it has been shown that one of these species has already been described as '' Ciona robusta''. By anthropogenic means, the species has invaded various parts of the world and is known as an invasive species. Although Linnaeus first categorised this species as a kind of mollusk, Alexander Kovalevsky found a tadpole-like larval stage during ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tunicates
A tunicate is a marine invertebrate animal, a member of the subphylum Tunicata (). It is part of the Chordata, a phylum which includes all animals with dorsal nerve cords and notochords (including vertebrates). The subphylum was at one time called Urochordata, and the term urochordates is still sometimes used for these animals. They are the only chordates that have lost their myomeric segmentation, with the possible exception of the 'seriation of the gill slits'. Some tunicates live as solitary individuals, but others replicate by budding and become colonies, each unit being known as a zooid. They are marine filter feeders with a water-filled, sac-like body structure and two tubular openings, known as siphons, through which they draw in and expel water. During their respiration and feeding, they take in water through the incurrent (or inhalant) siphon and expel the filtered water through the excurrent (or exhalant) siphon. Most adult tunicates are sessile, immobile and pe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rotifers
The rotifers (, from the Latin , "wheel", and , "bearing"), commonly called wheel animals or wheel animalcules, make up a phylum (Rotifera ) of microscopic and near-microscopic pseudocoelomate animals. They were first described by Rev. John Harris in 1696, and other forms were described by Antonie van Leeuwenhoek in 1703. Most rotifers are around long (although their size can range from to over ), and are common in freshwater environments throughout the world with a few saltwater species. Some rotifers are free swimming and truly planktonic, others move by inchworming along a substrate, and some are sessile, living inside tubes or gelatinous holdfasts that are attached to a substrate. About 25 species are colonial (e.g., '' Sinantherina semibullata''), either sessile or planktonic. Rotifers are an important part of the freshwater zooplankton, being a major foodsource and with many species also contributing to the decomposition of soil organic matter. Most species of the ro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
