• The major (U2) spliceosome removes majority of introns, while minute fraction of intron repertoire is processed by the minor (U12) spliceosome. (ijbs.com)
  • U12-type introns, minor spliceosome, insect evolution. (ijbs.com)
  • While introns from the first three groups undergo self-splicing, the latter endure splicing with the aid of complex machinery called spliceosome. (ijbs.com)
  • Coding sequences in eukaryotic genomes are frequently interrupted by spliceosomal introns, regions of noncoding DNA that are removed from pre-mRNA transcripts by the spliceosome, a complex of five RNAs and hundreds of proteins [ 1 ]. (biomedcentral.com)
  • iCLIP of spliceosome components reveals that PRPF8 depletion decreases RNP complex formation at most splice sites in exon-intron junctions throughout the genome. (biomedcentral.com)
  • Depending on whether the splicing process is autonomous or occurs through a riboprotein complex (the spliceosome ), a distinction is made between self-splicing and spliceosomal introns. (zxc.wiki)
  • These introns must be cut out through the spliceosome. (zxc.wiki)
  • The major spliceosome splices introns containing GU at the 5' splice site and AG at the 3' splice site. (wikidoc.org)
  • The minor spliceosome is very similar to the major spliceosome, however it splices rare introns with different splice site sequences. (wikidoc.org)
  • Self-splicing occurs for rare introns that form a ribozyme , performing the functions of the spliceosome by RNA alone. (wikidoc.org)
  • Group I and II introns perform splicing similar to the spliceosome without requiring any protein. (wikidoc.org)
  • This similarity suggests that Group I and II introns may be evolutionarily related to the spliceosome. (wikidoc.org)
  • In some eukaryotes a second 'minor' spliceosome is responsible for processing a tiny minority of introns. (nsf.gov)
  • We built a set T of flanking regions of genes with 1-3 introns from 21st and 22nd chromosomes extracted from GenBank to define positions having conserved properties, namely hydrophobicity, that are potentially essential for recognition by spliceosome. (ijbs.com)
  • The spliceosome recognizes conserved sequences at the exon-intron boundaries, namely the 5' splice site (5'ss) and the 3' splice site (3'ss). (ijbs.com)
  • The group II intron and the spliceosome share a common active site architecture and are thought to be evolutionarily related. (cornell.edu)
  • Most eukaryotic protein coding genes are intervened by non-coding sequences called introns ( Int ervening r egi ons ) [ 1 ], which are being removed from the primary transcript in the process of splicing [ 2 - 3 ]. (ijbs.com)
  • The non-intron sequences that become joined by this RNA processing to form the mature RNA are called exons. (wikipedia.org)
  • Although introns are sometimes called intervening sequences, the term "intervening sequence" can refer to any of several families of internal nucleic acid sequences that are not present in the final gene product, including inteins, untranslated regions (UTR), and nucleotides removed by RNA editing, in addition to introns. (wikipedia.org)
  • Nuclear pre-mRNA introns (spliceosomal introns) are characterized by specific intron sequences located at the boundaries between introns and exons. (wikipedia.org)
  • These sequences are recognized by spliceosomal RNA molecules when the splicing reactions are initiated. (wikipedia.org)
  • Apart from these three short conserved elements, nuclear pre-mRNA intron sequences are highly variable. (wikipedia.org)
  • By a bioinformatics analysis of intron sequences in other eukaryotes, the authors conclude that such splicing inefficiency is likely to be widespread, at least for short introns. (biomedcentral.com)
  • This machinery recognizes pre-mRNA sequences at several motifs - the 5′ and 3′ splice sites, the branch point, and polypyrimidine tracts - positioned at exon-intron boundaries [ 4 ]. (biomedcentral.com)
  • Any spliceosomal complex that forms during the splicing of a messenger RNA primary transcript to excise an intron that has canonical consensus sequences near the 5' and 3' ends. (yeastgenome.org)
  • The U12 introns were mapped onto the genomic sequences yielding 570 human and 182 Arabidopsis U12 validated intron positions available for comparative analysis (Additional file 1 ). (biomedcentral.com)
  • Probable orthologs were identified among human and Arabidopsis genes containing U12 introns by BLAST comparison, and the intron positions were mapped onto aligned protein sequences as previously described ([ 16 ] and Additional file 1 ). (biomedcentral.com)
  • The removal of non-coding sequences, or introns, from precursor messenger (m)RNAs and the ligation of coding sequences, or exons, a process called pre-mRNA splicing, is an essential step in gene expression. (fsu.edu)
  • The splice-site sequences of U2-type introns are highly degenerate, so many different sequences can function as U2-type splice sites. (ijbs.com)
  • Ferat, J.-L. & Michel, F. Group II self splicing introns in bacteria. (nature.com)
  • The self-splicing introns ( ribozymes ), which remove themselves from the mRNA, play a special role. (zxc.wiki)
  • There are two kinds of self-splicing introns, Group I and Group II . (wikidoc.org)
  • There are four main types of introns: tRNA introns, group I introns, group II introns, and spliceosomal introns (see below). (wikipedia.org)
  • Toor N, Zimmerly S, "Identification of a family of group II introns encoding LAGLIDADG ORFs typical of group I introns. (ucsd.edu)
  • Two transesterfications characterize the mechanism in which group I introns are sliced: 1) 3'OH of a free guanine nucleoside (or one located in the intron) or a nucleotide cofactor (GMP, GDP, GTP) attacks phosphate at the 5' splice site. (wikidoc.org)
  • The mechanism in which group II introns are spliced (two transesterfication reaction like group I introns) is as follows: 1)The 2'OH of a specific adenosine in the intron attacks the 5' splice site, thereby forming the lariat 2) The 3'OH of the 5' exon triggers the second transesterfication at the 3' splice site thereby joining the exons together. (wikidoc.org)
  • Although the widespread proliferation of introns in eukaryotic protein-coding genes remains one of the most poorly understood aspects of genomic architecture, major advances have emerged recently from large-scale genome sequencing projects and functional analyses of mRNA-processing events. (elsevierpure.com)
  • Introns are found in the genes of most organisms and many viruses and they can be located in both protein-coding genes and genes that function as RNA (noncoding genes). (wikipedia.org)
  • Introns were first discovered in protein-coding genes of adenovirus, and were subsequently identified in genes encoding transfer RNA and ribosomal RNA genes. (wikipedia.org)
  • For example, introns are extremely common within the nuclear genome of jawed vertebrates (e.g. humans, mice, and pufferfish (fugu)), where protein-coding genes almost always contain multiple introns, while introns are rare within the nuclear genes of some eukaryotic microorganisms, for example baker's/brewer's yeast (Saccharomyces cerevisiae). (wikipedia.org)
  • Spliceosomal introns often reside in eukaryotic protein-coding genes. (wikidoc.org)
  • For example, ~50% of the human genome consists of spliceosomal introns and non-LTR retroelements. (ucsd.edu)
  • Introns were initially thought to be entirely a feature of the eukaryotic genome. (pressbooks.pub)
  • Using our genome-wide BP database, we delineated the BP-ACC segments of all human introns and found extreme depletion of AG/YAG in the [BP+8, ACC-4] high-risk region. (bvsalud.org)
  • We created intronIC, a program for assigning intron class to all introns in a given genome, and used it on 24 eukaryotic genomes to create the Intron Annotation and Orthology Database (IAOD). (nsf.gov)
  • U2-type and U12-type introns, which are excised by the major and minor spliceosomes, respectively [ 7 - 8 ]. (ijbs.com)
  • Our observations suggest that Smu1 and RED relieve physical constraints arising from a short 5'SS-BS distance, thereby enabling spliceosomes to overcome structural challenges associated with the splicing of short introns. (mpg.de)
  • Spliceosomal introns are gene segments removed from RNA transcripts by ribonucleoprotein machineries called spliceosomes. (nsf.gov)
  • Different classes of introns are excised by the U2-type or the U12-type spliceosomes, large complexes of small nuclear ribonucleoprotein particles and associated proteins. (nsf.gov)
  • U2 snRNP-dependent introns make up the majority of all introns and are excised by spliceosomes containing the U1, U2, U4, U5 and U6 snRNPs. (ijbs.com)
  • U12 snRNP-dependent introns are the minor class of introns and are excised by spliceosomes containing U11, U12, U4atac, U6atac and U5 snRNPs. (ijbs.com)
  • Spliceosomes recognize and then remove regions called introns from immature mRNA molecules to help produce mature mRNA. (medlineplus.gov)
  • In other words, the identification of true orthology relationships between gene products now should progress beyond primary sequence and "splicing orthology", consisting in ancestrally shared exon-intron structures, is required to define orthologous isoforms at transcript level. (biomedcentral.com)
  • The exon/intron structures and genomic locus comparisons together with sequence phylogenetic analysis, suggested that urochordate serpins are classified into six groups (U1-U6), different from six groups (V1-V6) of vertebrate serpins. (jgenomics.com)
  • However, different types of introns were identified through the examination of intron structure by DNA sequence analysis, together with genetic and biochemical analysis of RNA splicing reactions. (wikipedia.org)
  • Evidence supports the idea that spliceosomal introns were not only present in the stem eukaryote but diverged into at least two distinct classes very early in eukaryotic evolution. (elsevierpure.com)
  • Insect genes that harbor U12-type introns belong to several functional categories among which proteins binding ions and nucleic acids are enriched and these few categories are also overrepresented among these genes that preserved minor type introns in Diptera . (ijbs.com)
  • Transfer RNA introns that depend upon proteins for removal occur at a specific location within the anticodon loop of unspliced tRNA precursors, and are removed by a tRNA splicing endonuclease. (wikipedia.org)
  • We demonstrate via RNAi coupled with RNA-Seq that two of these human-specific proteins, Smu1 and RED, function both as alternative splicing regulators and as general splicing factors and are required predominantly for efficient splicing of short introns. (mpg.de)
  • Since this RNA will be used to generate proteins, exons are denoted as coding regions, whereas introns are another example of non-coding material. (jove.com)
  • Introns are excised once the sequence is transcribed to mRNA, leaving only exons to code for proteins. (jove.com)
  • Introns play a role in the alternative splicing of a gene, so that a gene can produce several proteins that differ in sections. (zxc.wiki)
  • Thus, in neither conformer are the critical helices positioned to favor the proposed triplex interaction suggesting the obligation for other components, spliceosomal proteins, to facilitate and stabilize the catalytically active conformation. (cuny.edu)
  • These data suggest that although the central junction assumes a significant role in orienting helices, spliceosomal proteins and Mg 2+ facilitate formation of the catalytically active conformer. (cuny.edu)
  • No general function for spliceosomal introns has been demonstrated, and both their absence from prokaryotes and the recurrent massive loss of introns in various eukaryotic lineages suggests that no such essential function may exist. (biomedcentral.com)
  • Smu1 and RED are required for activation of spliceosomal B complexes assembled on short introns. (mpg.de)
  • This Smu1-RED requirement can be bypassed when the 5' and 3' regions of short introns are physically separated. (mpg.de)
  • An intron is any nucleotide sequence within a gene that is not expressed or operative in the final RNA product. (wikipedia.org)
  • The word intron is derived from the term intragenic region, i.e., a region inside a gene. (wikipedia.org)
  • The term intron refers to both the DNA sequence within a gene and the corresponding RNA sequence in RNA transcripts. (wikipedia.org)
  • A particularly extreme case is the Drosophila dhc7 gene containing a ≥3.6 megabase (Mb) intron, which takes roughly three days to transcribe. (wikipedia.org)
  • On the other extreme, a 2015 study suggests that the shortest known metazoan intron length is 30 base pairs (bp) belonging to the human MST1L gene. (wikipedia.org)
  • Instead, the numerous (average 2.3 per gene) and very short (average length 25 bp) introns of the ciliate Paramecium tetraurelia show a pronounced preference for interrupted reading frames: 81.3% of P. tetraurelia introns have a frameshift (that is, they are not a multiple of three base pairs), as opposed to the expected two-thirds frequency. (biomedcentral.com)
  • This intensifies the central mystery of eukaryotic gene structure: why did so many costly introns with no apparent function arise in the first place, and why are they retained in such a diverse array of species? (biomedcentral.com)
  • The few introns in Saccharomyces cerevisiae (only 0.05 per gene on average) show a previously mysterious bias towards ribosomal protein genes (0.74 introns per ribosomal gene). (biomedcentral.com)
  • Introns ( English Intr agenic regi ons ), the non-coding portions of the DNA within a gene (intragenic), adjacent exons separated. (zxc.wiki)
  • These results are compatible with the hypothesis that the high level of conservation of U12 intron positions and their persistence in genomes despite the unidirectional U12 to U2 conversion are explained by the role of the slowly excised U12 introns in down-regulation of gene expression. (biomedcentral.com)
  • While the size of the introns, number of introns per gene and the number of intron-containing genes can vary greatly between sequenced eukaryotic genomes, the structure of a gene with reference to intron presence and positions is typically conserved in closely related species. (biomedcentral.com)
  • Unexpectedly, the ABCB1 (ATP-Binding Cassette Subfamily B Member 1) gene which encodes a P-glycoprotein and underlies dwarfing traits in maize ( br2 ), sorghum ( dw3 ) and pearl millet ( d2 ) displayed considerable variation in intron composition. (biomedcentral.com)
  • An analysis of the ABCB1 gene structure in 80 angiosperms revealed that the number of introns ranged from one to nine. (biomedcentral.com)
  • Semiquantitative PCR showed that the M. guttatus ABCB1 gene copy without intron 7 had significantly lower transcript levels than the gene copy with intron 7. (biomedcentral.com)
  • Evolutionary loss and gain of introns in genomic sequence data may provide a mechanism by which organisms diversify gene expression and gene function. (biomedcentral.com)
  • We investigated twenty insect genomes in order to better understand the evolutionary dynamics of U12-type introns. (ijbs.com)
  • Although U12-type introns are highly conserved in specific lineages, they do undergo some evolutionary changes, for instance intron deletion or spliceosomal type switching [ 7 ]. (ijbs.com)
  • Thus there is strong evolutionary selection against 'read-through' introns that could be translated into protein. (biomedcentral.com)
  • In the episode Genesis (7x19) of the science fiction series Spaceship Enterprise: The Next Century , introns are presented as genetic evolutionary "remnants" that carry the genetic information of archetypes of species. (zxc.wiki)
  • However, the overall level of conservation of U12 introns between plants and animals, and hence the depth of the evolutionary conservation of U12 introns is not known. (biomedcentral.com)
  • Identifying minor introns in over 3000 eukaryotic genomes, we report diverse evolutionary histories including surprisingly high numbers in some fungi and green algae, repeated loss, as well as general biases in their positional and genic distributions. (nsf.gov)
  • These data constitute the most comprehensive view of minor introns and their evolutionary history to date, and provide a foundation for future studies of these remarkable genetic elements. (nsf.gov)
  • Nuclear pre-mRNA introns are often much longer than their surrounding exons. (wikipedia.org)
  • Introns are transcribed , but then from the pre-mRNA spliced out before them for translation from the nucleus is removed funneled. (zxc.wiki)
  • In genetics , splicing is a modification of genetic information after transcription , in which introns of precursor messenger RNA (pre-mRNA) are removed and exons of it are joined. (wikidoc.org)
  • Splicing of precursor messenger RNA is an essential process in eukaryotes in which the non-coding regions (introns) are removed and coding regions (exons) ligated together to form a mature mRNA. (cuny.edu)
  • Pre-mRNA splicing requires the bridging of the 5' and 3' ends of the intron. (embl.de)
  • There are at least two classes of pre-mRNA introns, based on the splicing machineries that catalyze the reaction. (ijbs.com)
  • However, subsequent processes remove introns from this transcript. (jove.com)
  • Abstract During nuclear maturation of most eukaryotic pre-messenger RNAs and long non-coding RNAs, introns are removed through the process of RNA splicing. (nsf.gov)
  • Most of eukaryotic genes are interrupted by introns that need to be removed from pre-mRNAs before they can perform their function. (ijbs.com)
  • Introns are rare in Bacteria and Archaea (prokaryotes), but most eukaryotic genes contain multiple splicesomal introns. (wikipedia.org)
  • The presence of non-coding introns is a characteristic feature of most eukaryotic genes. (biomedcentral.com)
  • The very short lengths of the introns in Paramecium also suggest a minor role, at most, in genomic stability, chromatin structure or in promoting recombination - other proposed advantages of introns. (biomedcentral.com)
  • A signature of genomic deletion of introns via NHEJ is the presence of 2-8 bp of micro-homology. (biomedcentral.com)
  • In addition, they contain a branch point, a particular nucleotide sequence near the 3' end of the intron that becomes covalently linked to the 5' end of the intron during the splicing process, generating a branched (lariat) intron. (wikipedia.org)
  • If introns are efficiently removed from transcripts before they are exported for translation, they should not respect coding meanings: whether or not an intron sequence contains a termination codon or a frameshift should be determined by chance. (biomedcentral.com)
  • Whether a sequence is recognized as an intron or an exon during splicing depends on the sequence. (zxc.wiki)
  • In addition, a third conserved intronic sequence that is known to be functionally important in splicing is the so-called branch point site (BPS) which is usually located very close to the end of the intron, at most 40 nucleotides before the terminal dinucleotide. (ijbs.com)
  • Some rough estimates of intron turnover rates are provided, and a testable hypothesis for the origin of new introns is proposed. (elsevierpure.com)
  • Cavalier-Smith, T. Intron phylogeny: A new hypothesis. (nature.com)
  • One common hypothesis is that introns impose only a small (or no) burden, and so are tolerated in many lineages. (biomedcentral.com)
  • Lynch, M & Richardson, AO 2002, ' The evolution of spliceosomal introns ', Current Opinion in Genetics and Development , vol. 12, no. 6, pp. 701-710. (elsevierpure.com)
  • Introns can be located at almost any point in the transcript, even in the middle of a block of three that functions as a codon in translation. (zxc.wiki)
  • In light of recent findings on the molecular natural history of splicing, various aspects of the phylogenetic and physical distributions of introns can now be interpreted in a theoretical framework that jointly considers the population-genetic roles of mutation, random genetic drift, and natural selection. (elsevierpure.com)
  • Splicing of all intron-containing RNA molecules is superficially similar, as described above. (wikipedia.org)
  • Toor N, Robart AR, Christianson J, Zimmerly S, "Self-splicing of a group IIC intron: 5' exon recognition and alternative 5' splicing events implicate the stem-loop motif of a transcriptional terminator. (ucsd.edu)
  • Intron mis-splicing: no alternative? (biomedcentral.com)
  • By knocking down a component of the NMD machinery, they revealed the intrinsic low efficiency of splicing for many introns and the essential role of NMD in preventing translation of the resulting unspliced transcripts. (biomedcentral.com)
  • First, the demonstrated inefficiency of splicing suggests that the presence of introns is even more disadvantageous to general fitness than previously appreciated. (biomedcentral.com)
  • Here, we show that alterations in RNA splicing patterns across the human transcriptome that occur in conditions of restricted cellular PRPF8 abundance are defined by the altered splicing of introns with weak 5′ splice sites. (biomedcentral.com)
  • Since in prokaryotic genomes introns do not exist, splicing naturally only occurs in eukaryotes . (wikidoc.org)
  • The type of splicing depends on the structure of the spliced intron and the catalysts required for splicing to occur. (wikidoc.org)
  • Within the intron, a 3' splice site, 5' splice site, and branch site are required for splicing. (wikidoc.org)
  • Similarly, on comparing rhb1 I1 and rhb1 I1 with 10BrP ten minitranscripts, we detected a higher dependence of your variant intron on SpSlu7 for its efficient splicing (Fig. 8A, panels i and iii, lane four). (nrtisinhibitor.com)
  • These data contrasted using the in vitro dispensability of budding yeast ScSlu7 for splicing of ACT1 intron variants having a BrP-to-3=ss Brd Inhibitor Species distance significantly less than 7 nt (twelve). (nrtisinhibitor.com)
  • Lack of microhomology in the exon upstream of lost phase I introns was likely due to release of the selective constraint on the penultimate base (3rd base in codon) of the terminal codon by the splicing machinery. (biomedcentral.com)
  • U2AF1 belongs to the SR family of splicing factors and is involved in the removal of introns from mRNAs and exon-exon binding. (bvsalud.org)
  • Interestingly, splicing was changed at limited levels in the deletion strains, while large amounts of differentially-expressed genes and alternative polyadenylation events were identified, showing preferences in the down-regulation of genes with 1-2 introns and selection of proximal sites for 3'-end polyadenylation. (bvsalud.org)
  • Third, no association of intron splicing with cell proliferation in a minor intron-rich fungus suggests that regulatory roles are lineage-specific and thus cannot offer a general explanation for minor splicing's persistence. (nsf.gov)
  • Structural basis for the second step of group II intron splicing. (cornell.edu)
  • exon form, immediately preceding the second step of splicing, analogous to the spliceosomal P complex. (cornell.edu)
  • Aberrant splicing of U12-type introns has been shown to be a hallmark feature of MDS with ZRSR2 mutations. (cornell.edu)
  • We further demonstrated that intron 7 carried two motifs that were highly conserved across the monocot-dicot divide. (biomedcentral.com)
  • The fact that genes were split or interrupted by introns was discovered independently in 1977 by Phillip Allen Sharp and Richard J. Roberts, for which they shared the Nobel Prize in Physiology or Medicine in 1993. (wikipedia.org)
  • Introns are now known to occur within a wide variety of genes throughout organisms, bacteria, and viruses within all of the biological kingdoms. (wikipedia.org)
  • Both of these are considered to have evolved from a class of introns which orginated in bacteria billions of years ago called the group II introns. (ucsd.edu)
  • In recent years the presence of intron-containing genes has been documented in archaea, bacteriophages, and even some bacteria. (pressbooks.pub)
  • In contrast, the mitochondrial genomes of vertebrates are entirely devoid of introns, while those of eukaryotic microorganisms may contain many introns. (wikipedia.org)
  • We estimate that ancestral minor intron densities were comparable to those of vertebrates, suggesting a trend of long-term stasis. (nsf.gov)
  • showed that introns in ribosomal protein genes, but not introns in other genes, are inefficiently spliced under aminoacid starvation, resulting in reduced production of protein-encoding spliced transcripts and thus presumably inhibiting ribosome formation and overall protein translation. (biomedcentral.com)
  • All introns in ABCB1 underwent either a one-time loss (single loss in one lineage/species) or multiple independent losses (parallel loss in two or more lineages/species) with the majority of losses occurring within the grass family. (biomedcentral.com)
  • Intron 7, the longest intron, was lost in only a single species, Mimulus guttatus , following duplication of ABCB1 . (biomedcentral.com)
  • This is mostly the result of intron deletion, but in a number of dipteral cases, minor type introns were switched to a major type, as well. (ijbs.com)
  • Two main mechanisms for intron loss have been proposed, that is reverse transcription (RT)-mediated intron loss and intron deletion triggered by repair of double strand breaks (DSBs) via non-homologous end joining (NHEJ). (biomedcentral.com)
  • We observed an identical exon/intron structure for 32% of human and mouse orthologous genes. (biomedcentral.com)
  • We report that the positions of minor, U12 introns are conserved in orthologous genes from human and Arabidopsis to an even greater extent than the positions of the major, U2 introns. (biomedcentral.com)
  • It has been suggested that a few mutations in the donor SS of U12-type intron may change the intron type to the major one. (ijbs.com)
  • The minor spliceosomal system has been lost independently in some lineages, while in some others few U12-type introns persist. (ijbs.com)
  • Gilbert 1978) The term intron also refers to intracistron, i.e., an additional piece of DNA that arises within a cistron. (wikipedia.org)
  • must be replaced by that of a transcription unit containing regions which will be lost from the mature messenger - which I suggest we call introns (for intragenic regions) - alternating with regions which will be expressed - exons. (wikipedia.org)
  • Additionally, U12-type introns lack a polypyrimidine tract between the BPS and the 3′ splice site. (ijbs.com)
  • We attempted to distinguish U2 and U12-types introns with help of hydrophobicity profiles on sets of spice sites for U2 or U12-type introns extracted from SpliceRack database. (ijbs.com)
  • Because of the stronger signal constrain at the 5´ SS of U12-type introns, this process is believed to be unidirectional, as switching intron type from U2 to U12 would require too many concurrent changes [ 7 , 14 , 16 ]. (ijbs.com)
  • We analyzed the available data on U12 introns in human and Arabidopsis thaliana genomes in order to systematically compare their conservation with that of U2 introns. (biomedcentral.com)
  • Toor N, Hausner G, Zimmerly S, "Coevolution of group II intron RNA structures with their intron-encoded reverse transcriptases. (ucsd.edu)
  • The U12-type introns were discovered in the early 1990s thanks to atypical splice site (SS) dinucleotides AT-AC [ 8 ]. (ijbs.com)
  • U12-type introns can be flanked by different terminal dinucleotides indicating that the donor and acceptor sites are degenerate [ 14 ]. (ijbs.com)
  • Finally, three findings suggest a major role for neutral processes in minor intron evolution. (nsf.gov)
  • The frequency of introns within different genomes is observed to vary widely across the spectrum of biological organisms. (wikipedia.org)
  • Two genetic elements particularly abdundant in these organisms are introns and retroelements. (ucsd.edu)