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PubMed2004

Adaptive immunity is the primary force driving selection of equine infectious anemia virus envelope SU variants during acute infection.

Equine infectious anemia virus (EIAV) is a lentivirus that causes persistent infection in horses. The appearance of antigenically distinct viral variants during recurrent viremic episodes is thought to be due to adaptive immune selection pressure. To test this hypothesis, we evaluated envelope SU cloned sequences from five severe combined immunodeficient (SCID) foals infected with EIAV. Within the SU hypervariable V3 region, 8.5% of the clones had amino acid changes, and 6.4% had amino acid changes within the known cytotoxic T lymphocyte (CTL) epitope Env-RW12. Of all the SU clones, only 3.1% had amino acid changes affecting potential N-linked glycosylation sites. In contrast, a much higher degree of variation was evident in SU sequences obtained from four EIAV-infected immunocompetent foals. Within V3, 68.8% of the clones contained amino acid changes, and 50% of the clones had amino acid changes within the Env-RW12 CTL epitope. Notably, 31.9% of the clones had amino acid changes affecting one or more glycosylation sites. Marked amino acid variation occurred in cloned SU sequences from an immune-reconstituted EIAV-infected SCID foal. Of these clones, 100% had amino acid changes within V3, 100% had amino acid changes within Env-RW12, and 97.5% had amino acid changes affecting glycosylation sites. Analysis of synonymous and nonsynonymous nucleotide substitutions revealed statistically significant differences between SCID and immunocompetent foals and between SCID foals and the reconstituted SCID foal. Interestingly, amino acid selection at one site occurred independently of adaptive immune status. Not only do these data indicate that adaptive immunity primarily drives the selection of EIAV SU variants, but also they demonstrate that other selective forces exist during acute infection.

Acute Disease↗

PubMed2006

Genetic variants of the ADPRT, XRCC1 and APE1 genes and risk of cutaneous melanoma.

Sunlight causes various kinds of DNA damage, including oxidative lesions that are removed effectively by the base excision repair (BER) pathway, in which ADPRT, XRCC1 and APE1 play a key role. However, genetic variation in these genes may alter their functions. We hypothesized that ADPRT, XRCC1 and APE1 polymorphisms are associated with risk of cutaneous melanoma (CM). In a hospital-based case-control study of 602 CM patients and 603 cancer-free control subjects frequency matched on age, sex and ethnicity, we genotyped for three non-synonymous single nucleotide polymorphisms (SNPs) (i.e. the ADPRT Val762Ala, XRCC1 Arg399Gln and APE1Asp148Glu) and assessed their associations with risk of CM. We found no significant difference in the allele frequencies between cases and controls for any of these three SNPs. However, we found that, compared with the APE1 Asp/Asp genotype, a significantly decreased risk of CM was associated with the APE1 Asp/Glu [adjusted odds ratio (OR), 0.60; 95% confidence interval (CI), 0.41-0.86], Glu/Glu (OR, 0.58; 95% CI, 0.38-0.88) and combined APE1 Asp/Glu+Glu/Glu (OR, 0.59; 95% CI, 0.42-0.83) genotypes, but not for other XRCC1 variant genotypes. Moreover, there was evidence for a possible gene-gene interaction between XRCC1 and APE1 variants in the association with risk of CM (P=0.030). We conclude that the APE1 Glu variant may have an effect or interact with XRCC1 in the etiology of CM or in linkage disequilibrium with other untyped protective alleles. Larger studies with more SNPs in the BER genes are needed to verify these findings.

Adult↗

PubMed1994

Molecular and population genetic analysis of allelic sequence diversity at the human beta-globin locus.

Allelic sequence polymorphism at the beta-globin locus was investigated in a group of 36 Melanesians. A 3-kilobase fragment containing the gene and its flanking regions was sequenced in 60 normal (beta A) and 12 thalassemic (intron 1, position 5, G-->C) chromosomes. Haplotype relationships between linked polymorphisms were derived by allele-specific PCR amplification and sequencing. Seventeen nucleotide polymorphisms and 2 length variants were identified, and these sites segregated as 17 sequence haplotypes in the normal chromosomes. This haplotype diversity is higher than that expected on the basis of the nucleotide polymorphism observed and is probably due to recombination and gene conversion. Nucleotide diversity at synonymous sites in the sample is 0.14%, suggesting an average age of sequence divergence of approximately 450,000 years, consistent with that expected for a neutrally evolving human nuclear locus.

Alleles↗

PubMed1995

Molecular basis of polymorphism at the esterase-5B locus in Drosophila pseudoobscura.

Sequence variation was studied in a 2.2-kb region encompassing the esterase-5B locus in Drosophila pseudoobscura from two California populations. In these populations, two common electrophoretic classes and many less frequent variants occur, and it was formerly shown by KEITH (1983) that allele frequencies differed from random distribution under an infinite allele model. Nucleotide polymorphisms were determined in 16 sequences representing 14 electrophoretic classes. There was no significant sequence differentiation between populations, and both synonymous and nonsynonymous polymorphisms are distributed homogeneously along the sequence. The data show that the two major electrophoretic classes are heterogeneous at the amino acid level with no diagnostic amino acid(s) distinguishing them. At the nucleotide level, members of one major class are more similar to members of other electrophoretic classes than they are to each other. It appears that random combinations of the neutral amino acid polymorphisms and other undefined physical properties of the proteins generate the different electrophoretic classes and maintain considerable variation at Est-5B.

Amino Acid Sequence↗

PubMed2002

Fine mapping of the chromosome 2p12-16 dyslexia susceptibility locus: quantitative association analysis and positional candidate genes SEMA4F and OTX1.

A locus on chromosome 2p12-16 has been implicated in dyslexia susceptibility by two independent linkage studies, including our own study of 119 nuclear twin-based families, each with at least one reading-disabled child. Nonetheless, no variant of any gene has been reported to show association with dyslexia, and no consistent clinical evidence exists to identify candidate genes with any strong a priori logic. We used 21 microsatellite markers spanning 2p12-16 to refine our 1-LOD unit linkage support interval to 12cM between D2S337 and D2S286. Then, in quantitative association analysis, two microsatellites yielded P values<0.05 across a range of reading-related measures (D2S2378 and D2S2114). The exon/intron borders of two positional candidate genes within the region were characterized, and the exons were screened for polymorphisms. The genes were Semaphorin4F (SEMA4F), which encodes a protein involved in axonal growth cone guidance, and OTX1, encoding a homeodomain transcription factor involved in forebrain development. Two non-synonymous single nucleotide polymorphisms were found in SEMA4F, each with a heterozygosity of 0.03. One intronic single nucleotide polymorphism between exons 12 and 13 of SEMA4F was tested for quantitative association, but no significant association was found. Only one single nucleotide polymorphism was found in OTX1, which was exonic but silent. Our data therefore suggest that linkage with reading disability at 2p12-16 is not caused by coding variants of SEMA4F or OTX1. Our study outlines the approach necessary for the identification of genetic variants causing dyslexia susceptibility in an epidemiological population of dyslexics.

Chromosome Mapping↗

PubMed2003

Natural allelic variants of breast cancer resistance protein (BCRP) and their relationship to BCRP expression in human intestine.

The aim of this study was to identify the extent of genetic variability in breast cancer resistance protein (BCRP) in humans. We first analysed the sequence of BCRP cDNA from human livers and from human intestines phenotyped for expression of intestinal BCRP. We then determined the frequency of all known coding single nucleotide polymorphisms (cSNPs) using DNA from individuals representing 11 different ethnic populations. Nine SNPs including four non-synonymous and three synonymous cSNPs and two intronic SNPs were identified. Of the missense mutations, exon 2 SNP (G34A) resulted in a V12M change; exon 5 SNP (C421A) resulted in a Q141K substitution; exon 6 SNP (A616C) resulted in an I206L amino acid substitution; and exon 15 SNP (A1768T) resulted in a N590Y change in the BCRP protein. The two most frequent polymorphisms identified in the human population studied were the G34A and C421A transitions. There was marked variation in BCRP genotypes and allele frequencies in the different populations. BCRP mRNA was phenotyped in human small bowel intestinal samples by real-time polymerase chain reaction and BCRP protein was analysed on immunoblots of tissue from the same individuals. There was a 78-fold variation in expression of BCRP mRNA and significant variation in BCRP protein expression in human intestine. Expression of intestinal BCRP mRNA and protein was not different between persons expressing the common Gln141 allele compared to the Lys141 allele. Thus, common natural allelic variants of BCRP have been identified, and did not influence interindividual variation in expression of BCRP mRNA in human intestine, but remain to be tested for their effect on BCRP function.

ATP Binding Cassette Transporter, Subfamily G, Mem↗

PubMed2004

Molecular evolution of the phytochrome gene family in sorghum: changing rates of synonymous and replacement evolution.

The photoreceptor phytochromes, encoded by a small gene family, are responsible for controlling the expression of a number of light-responsive genes and photomorphogenic events, including agronomically important phenotypes such as flowering time and shade-avoidance behavior. The understanding and control of flowering time are particularly important goals in sorghum cultivar development for diverse environments, and naturally occurring variation in the phytochrome genes might prove useful in breeding programs. Also of interest is whether variation observed at the phytochrome loci in domesticated sorghum, or in particular races, is a result of human selection. Population genetic studies can reveal evidence of such selection in patterns of polymorphism and divergence. In this study we report a population genetic analysis of the PHY gene family in Sorghum bicolor (L.) Moench in a diverse panel including both cultivated and wild accessions. We show that the level of nucleotide variation in all gene family members is about half the average for this species, consistent with purifying selection acting on these loci. However, the rate of amino acid substitution is accelerated at PHYC compared to the other two loci. In comparisons to a closely related sorghum species, PHYC shows a pattern of intermediate frequency amino acid changes that differ from the patterns observed in comparisons across longer evolutionary distances. There is also a departure from expected patterns of polymorphism and divergence at synonymous sites in PHYC, although the data do not fit a simple model of directional or diversifying selection. Cultivated sorghum has a level of variation similar to that of wild relatives (ssp. verticilliflorum), but many polymorphisms are subspecies-specific, including several amino acid variants.

Amino Acid Sequence↗

PubMed1998

Quasispecies nature of three maize streak virus isolates obtained through different modes of selection from a population used to assess response to infection of maize cultivars.

Three maize streak virus (MSV) isolates were derived from an MSV population used to assess the response to infection of maize cultivars. Isolate SP1 was obtained from this population through short acquisition and inoculation periods (1 and 5 min, respectively), using a single Cicadulina mbila vector. Isolate SP2 was derived from SP1 after transmission to a wild perennial host (Coix lacryma-jobi), on which it was maintained for about 4 years without insect transmission. Isolate N2A, the most pathogenic isolate, was obtained from the initial population after serial passages on almost completely resistant inbred maize lines. The complexity of each isolate was analysed by RFLP analysis and sequencing based on 120 SP1 clones, 36 SP2 clones and 40 N2A clones. All three isolates were composed of different but related clones, consistent with a quasispecies structure. The mutations were distributed throughout the genome. Mutation frequencies, based on all available sequences, were 3.8 x 10(-4) for SP1, 10.5 x 10(-4) for SP2 and 6.9 x 10(-4) for N2A. As expected from the bottleneck selection step, the intra-isolate variability of SP1 was relatively low. Comparison between SP1 and SP2 showed that SP1 heterogeneity increased during maintenance on the wild host. Furthermore, the consensus sequences of SP1 and SP2 differed by two non-synonymous substitutions in the complementary sense gene repA. N2A had a relatively low degree of heterogeneity, but was composed of several sub-populations. The results reflect the influence of the mode of selection of MSV isolates on their quasispecies organization, i.e. distribution of variants, and master sequence.

Base Sequence↗

PubMed2004

Natural selection and the organ-specific differentiation of HIV-1 V3 hypervariable region.

The existence of organ-specific HIV-1 populations within infected hosts has been studied for many years; nonetheless results reported by different authors are somewhat discrepant. To tackle this problem, we used a population genetics approach to analyze previously published data from the V3 hypervariable region of the envelope env gene. Our results are compatible with a population subdivision by organs in 95% of individuals analyzed at autopsy. In addition, populations infecting the nervous system and testicles clearly appear as differentiated subsets of the so-called macrophage-tropic variants. Liver and kidney may harbor differentiated populations as well. Although it is widely accepted that organ compartmentalization arises as a consequence of different selective pressures imposed by different organs, a definitive demonstration has not yet been provided. Our analysis of the pattern of synonymous and nonsynonymous nucleotide substitutions provides evidence supporting this hypothesis, without discarding the role of other evolutionary processes. In contrast, positive selection does not seem to be the mechanism responsible for the evolution of patient-specific sequences.

Analysis of Variance↗

PubMed1984

Interaction of Vicia graminea anti-N lectin with cell surface glycoproteins from erythrocytes with rare blood group antigens.

The erythrocyte receptors for Vicia graminea (Vg) anti-N lectin have been investigated after 125I-labelling of the purified lectin and binding to membrane components separated by dodecyl sulphate polyacrylamide gel electrophoresis. GP alpha (synonym glycophorin A or MN glycoprotein) and GP delta (synonym glycophorin B or Ss glycoprotein) are the main Vg receptors of native human blood group NN and MN erythrocytes whereas Vg lectin only binds to GP delta from MM red cells. The glycoprotein of 28 kDa present in Mi III erythrocytes (a presumed variant of GP delta) carries Vg receptors. Both binding studies and agglutination experiments with this lectin suggest that the delta Mi III gene might produce more glycoprotein molecules than the normal delta gene. Binding of Vg lectin to hybrid glycoproteins [from Mi V, St(a+) and Dantu (+) donors] produced by unequal crossing-over between alpha and delta genes, may occur if the molecules exhibit N activity. The lectin does not bind to sialic acid- and galactose-deficient glycoproteins from Tn erythrocytes and no binding could be detected in the region of GP delta of erythrocytes from S-s-U-individuals. Addition of N-acetylgalactosamine residues to the alkali-labile oligosaccharides attached to GP alpha and GP delta, as found in Cad erythrocytes, decrease the binding capacity for Vg lectin. Finally the absence of Vg lectin binding sites on native GP alpha molecule from MgMg and McM erythrocytes, which carry well defined variants of this glycoprotein, supports the view that the binding site of the lectin on native glycoproteins is located at the N-terminal end of glycoprotein (GP alpha and GP delta) with N specificity (N-terminus = Leu).

Antigens, Surface↗

PubMedDate not supplied

Nevus roseus: a distinct vascular birthmark.

The new term nevus roseus is proposed to denote a lateralized telangiectatic birthmark with a light-red or pale-pink color, unlike the dark hue of nevus flammeus. It appears to be a distinct entity rather than just a color variant of nevus flammeus. Remarkably, nevus flammeus is a characteristic component of phacomatosis pigmentovascularis type II ("phacomatosis cesioflammea"), whereas nevus roseus represents a distinguishing feature of phacomatosis pigmentovascularis type III ("phacomatosis spilorosea"). In analogy to "port-wine stain" that is used as a synonym for nevus flammeus, nevus roseus could also be called "rosé-wine stain". This lateralized vascular birthmark should be distinguished from the salmon patch that always involves the midline of the body. Nevus roseus belongs to the rather broad category of telangiectatic nevi, as well as to the even larger group of "capillary malformations". For obvious reasons these terms are not suitable to designate any specific type of vascular birthmark such as nevus roseus.

Adult↗

PubMed2004

Contrasting modes of natural selection acting on pigmentation genes in the Drosophila dunni subgroup.

Genes that encode for divergent adaptive traits may have genealogies that contrast with those from loci that are not functionally involved in differentiation. Here, we examine DNA sequence variation among the species of the eastern Caribbean Drosophila dunni subgroup at two loci, yellow and dopa decaboxylase (Ddc), which both play integral roles in pigmentation patterning of adult Drosophila. Phylogenetic analyses of these loci produce gene genealogies with topologies that mirror those described for other nuclear genes: the six morphologically distinct species within the subgroup are divided into only three lineages, with one lineage containing four species that share extensive ancestral polymorphism. At the Ddc locus these major lineages are delineated only by silent site variation. We observe a significantly higher rate of synonymous site divergence than non-synonymous divergence, consistent with strong purifying selection acting on the locus. In contrast, the yellow locus exhibits patterns of amino acid divergence and nucleotide diversity that are consistent with recent diversifying selection acting in two different lineages. This selection appears to be targeting amino acid variants in the signal sequence of the Yellow protein, a region which is tightly constrained among members of the larger D. cardini radiation. This result highlights not only the potential importance of yellow in the evolution of divergent pigmentation patterns among members of the D. dunni subgroup, but also hints that variation in signal peptide sequences may play a role in phenotypic diversification.

Amino Acid Sequence↗

PubMed2006

Single amino-acid InDel variants generated by alternative tandem splice-donor and -acceptor selection.

We have investigated putative single amino-acid InDel variants with human ESTs. Examination of the formation process for single amino-acid InDel variants indicates a possible splicing mechanism in addition to the genomic insertion/deletion events as would be expected. The wobble-splicing transcripts were often generated around the intron-exon boundaries by selecting an alternative neighboring splice signal sequence, in particular the tandem agNAG or GTNgt sequence at the splice-acceptor or -donor site, thus creating single amino-acid InDel isoforms. Another category of variants was identified with one altered amino-acid plus one amino-acid InDel, under divergent coding-frame usage. We demonstrate that such minute distance of splice site choice generates an even greater level of transcriptome diversity, and suggest that non-functional synonymous or intronic SNPs could be converted to functionally significant InDel alterations through this process. This subtle alteration in mRNA and protein-coding sequence may elicit a great impact upon human genome and proteome diversity.

Alternative Splicing↗

PubMed2026

Genome-wide variation analysis of two Salvia hispanica L. genotypes and implication for associations with metabolic and adaptive traits.

BACKGROUND: Advances in next-generation sequencing have accelerated genome-wide exploration of genetic diversity in underutilized oilseed crops. Salvia hispanica L. (chia), a high-nutrient pseudocereal rich in omega-3 fatty acids, is increasingly valued for its health benefits and commercial potential, yet it remains poorly characterized at the genomic level. Understanding the scale and nature of genomic variation is essential for improving complex traits such as oil yield, stress tolerance, and seed quality. METHODS: Two contrasting chia genotypes, Black-chia (CACH-B) and White- chia (CACH-W), were resequenced using the Bio-Resequencing Toolkit (BRT) pipeline. High-coverage sequencing, with a mapping rate exceeding 99% and an average depth of approximately 28×, facilitated the detection and annotation of single-nucleotide polymorphisms (SNPs), insertions and deletions (InDels), copy-number variations (CNVs), and structural variants (SVs). The functional classification of variant impacts enabled the identification of genes potentially linked to metabolic and adaptive traits. RESULTS: A total of 1.97 million SNPs, 401,493 InDels, 836 CNVs, and 15,288 SVs were identified across the chia genome. Notably, approximately 53% of exonic SNPs were non-synonymous (dN/dS ≈ 1.28), predominantly affecting lipid metabolism, transcriptional regulation, and stress response pathways, potentially altering key agronomic traits. In addition, CNV hotspots were concentrated in chromosomes 3 and 6, overlapping MYB, WRKY, and bZIP transcription factor loci, may potentially be involved in stress tolerance and yield. Furthermore, structural rearrangements, including inversions and duplications within the FAD2, FAD3, and CYP450 gene clusters, were potentially associated with seed pigmentation and omega-3 biosynthesis, pointing to their potential breeding relevance. Observed heterozygosity (Hₒ ≈ 0.71) and nucleotide diversity (π ≈ 7 × 10-3) indicated moderate to high allelic richness. In addition, the low FST value (0.038) indicates substantial genomic similarity between the two genotypes. CONCLUSION: This study presents the first comprehensive map integrating SNPs, CNVs, and SVs in S. hispanica L. The results reveal a structurally dynamic genome characterized by substantial sequence and structural variation, providing valuable insights into genomic diversity and potential adaptive mechanisms in chia. The coexistence of high SNP diversity and abundant structural variation underpins chia's nutritional specialization and environmental resilience. These results deliver a foundational genomic resource for marker-assisted breeding, genome-wide association studies, and the development of climate-resilient chia cultivars.

Copy-number variation, structural variation↗

PubMed2002

Phylogenetic evidence for frequent positive selection and recombination in the meningococcal surface antigen PorB.

Previous estimates of rates of synonymous (d(S)) and nonsynonymous (d(N)) substitution among Neisseria meningitidis gene sequences suggested that the surface loops of the variable outer membrane protein PorB were under only weak selection pressure from the host immune response. These findings were consistent with studies indicating that PorB variants were not always protective in immunological and microbiological assays and questioned the suitability of this protein as a vaccine component. PorB, which is expressed at high levels on the surface of the meningococcus, has been implicated in mechanisms of pathogenesis and has also been used as a typing target in epidemiological investigations. In this work, using more precise estimates of selection pressures and recombination rates, we have shown that some residues in the surface loops of PorB are under very strong positive selection, as great as that observed in human immunodeficiency virus-1 surface glycoproteins, whereas amino acids within the loops and the membrane-spanning regions of the protein are under purifying selection, presumably because of structural constraints. Congruence tests showed that recombination occurred at a rate that was not sufficient to erase all phylogenetic similarity and did not greatly bias selection analysis. Homology models of PorB structure indicated that many strongly selected sites encoded residues that were predicted to be exposed to host immune responses, implying that this protein is under strong immune selection and requires further examination as a potential vaccine candidate. These data show that phylogenetic inference can be used to complement immunological and biochemical data in the choice of vaccine candidates.

Amino Acid Sequence↗

PubMed1990

Computer diagnosis of skin disease.

A transferable computer program for the differential diagnosis of diseases of the skin, CLINDERM, has been produced for use by physicians on standard IBM and compatible personal microcomputers. This program lists the differential diagnosis and definitive diagnosis of any presented disease of the skin, except single tumors. The physician operator indicates the distribution and detailed description of lesions, which the interactive system integrates with a comprehensive knowledge base. The computer diagnosis in 129 cases was compared with independent interpretation of the same information by an academic dermatologist. Results were synonymous in 66.7% of all diseases and similar in an additional 4.7%. A common differential diagnosis was obtained in 24%, for a 95.3% rate of synonymous, similar, or common differential diagnoses. Diagnosis was different in 3.9% and description was inadequate for diagnosis in 0.8%. The variation in diagnosis showed that some descriptive terms are prejudicial of certain diagnoses; that diagnostic terms are not all completely standardized; that some diagnoses are variants of another disease; and that drug-induced eruptions simulate many other diseases. A skin disease can usually be diagnosed by specific description. Most lesions that are not diagnostic from inspection are nodular. A computer can be programmed to list diagnoses according to morphologic description.

Dermatology↗

PubMed2006

Two novel presenilin 1 gene mutations connected with frontotemporal dementia-like clinical phenotype: genetic and bioinformatic assessment.

Mutations in the amyloid precursor protein (APP), presenilin 1 (PSEN1) and presenilin 2 (PSEN2) genes are associated with early-onset familial Alzheimer's disease (EOAD). There are several reports describing mutations in PSEN1 in cases with frontotemporal dementia (FTD). We identified two novel mutations in the PSEN1 gene: L226F and L424H. The first mutation was detected in a patient with a clinical diagnosis of FTD and a post-mortem diagnosis of AD. The second mutation is connected with a clinical phenotype of variant AD with strong FTD signs. In silico modeling revealed that the mutations, as well as mutations used for comparison (F177L and L424R), change the local structure, stability and/or properties of the transmembrane regions of the presenilin 1 protein (PS1). In contrast, a silent non-synonymous substitution F175S is eclipsed by external residues and has no influence on PS1 interfacial surface. We suggest that in silico analysis of PS1 substitutions can be used to characterize novel PSEN1 mutations, to discriminate between silent polymorphisms and a potential disease-causing mutation. We also propose that PSEN1 mutations should be considered in FTD patients with no MAPT mutations.

Adult↗

PubMed1998

The evolution of the alcohol dehydrogenase gene family by loss of introns in plants of the genus Leavenworthia (Brassicaceae).

We present results showing that several species in the plant genus Leavenworthia, in the Brassica family, have three alcohol dehydrogenase loci, unlike Arabidopsis thaliana, which has only a single classical (class P) alcohol dehydrogenase locus. Based on a portion of the sequence, the alcohol dehydrogenase loci of Leavenworthia show about 92%-93% amino acid sequence identity to that of the A. thaliana alcohol dehydrogenase. The great majority of the sequence differences from the A. thaliana Adh-coding sequence, and also between three different Leavenworthia species, are synonymous, suggesting that all are currently functional (or have been in the recent evolutionary past). The loci differ in the numbers of introns present, with one locus (Adh-3) having no introns present. RT-PCR tests detect expression of all three loci. Linkage data using variant alleles identified by single-strand conformation polymorphism analysis show that the three Leavenworthia loci are not closely linked. The results therefore suggest that the Adh-3 locus may have arisen via an mRNA intermediate but, despite loss of the introns, is expressed.

Alcohol Dehydrogenase↗