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At least 19 recordsLinked to original sources
PubMed1975

[Molecular evolution].

The molecular evolution is considered in several protein families. It can be studied with the data of an entirely known structure, like in hemoglobin or cytochrome, or of only partial structural data, as for proteases or immunoglobulins. In the case of isozymes the study of physico-chemical and kinetic properties is more indirect. Finally, it is shown that the molecular mechanisms are always the same, happening probably at the same frequency, the differences being due to a variable selection by molecular constraints and adaptation to the environment.

Biological Evolution↗
PubMed2025

Molecular evolution of the members of the Snq2/Pdr18 subfamily of Pdr transporters in the Hemiascomycete yeasts.

The transporters of the ATP-Binding Cassette (ABC) Superfamily involved in the Multidrug Resistance (MDR) phenomena are also known as ABC-Pleiotropic Drug Resistance (PDR) proteins. The homologs of the Saccharomyces cerevisiae SNQ2 and PDR18 genes were identified in 171 yeast genomes, representing 68 different hemiascomycetous species. All early-divergent yeast species analyzed in this work lack Snq2/Pdr18 homologs, suggesting that the origin of these ABC-PDR genes in hemiascomycete yeasts resulted from a horizontal transfer event. The evolutionary pathway of the Snq2/Pdr18 protein subfamily in pathogenic Candida species was also reconstructed, revealing a main gene lineage leading to the Candida albicans SNQ2 gene. The results indicate that, after the gene duplication event at the origin of the SNQ2/PDR18 paralogs, the PDR18 ortholog has been under strong diversifying selection and suggest that a small portion of the sequence of the SNQ2 ancestral ortholog might have been under mild positive selection. The results also showed that strong positive selection was exerted over one of the two paralogs generated by the Whole Genome Duplication (WGD) event, corresponding to the duplicate at the origin of a "short-lived" WGD sublineage.

Evolution, Molecular↗
PubMed2026

Mapping the Molecular Evolution and Role of Wild Rice GLYIII Protein-Encoding Genes in Abiotic Stress Response.

To address the need for sustainable food production amid rapid global climate change, developing rice varieties that grow optimally even under harsh conditions is essential. An effective approach in this direction would be to harness the stress resilience traits of the crop wild relatives (CWRs) of rice. Among the various crucial stress-responsive genes, the Glyoxalase III (GLYIII) gene family is of utmost importance for its ability to detoxify the toxic glycolytic byproduct, methylglyoxal (MG), in a less energy-intensive, single-step process, as well as for its multifaceted cytoprotective role. In our study, a comprehensive genome-wide search across the Oryza genus revealed that GLYIII genes are conserved across wild rice genotypes. Their number has expanded during domestication, driven by gene duplications. Interestingly, only a few orthologous pairs showed positive selection, suggesting that the functions of most others need to be constrained and or conserved.We found that higher GLYIII activity, Total Antioxidant Capacity, endogenous glutathione (GSH) levels, and free radical scavenging activity contributes to the stress resilience of wild rices O. punctata, O. meridionalis, and O. nivara, in addition to other factors. , , . , . Our qRT-PCR analysis revealed differential expression of the OpGLYIII, OmGLYIII, and OnGLYIII genes across different developmental stages and in response to various abiotic stresses. Furthermore, we report that wild rice GLYIII proteins, specifically OpGLYIII-3, OmGLYIII-3, and OnGLYIII-5, exhibit high catalytic efficiency over a broad pH range and at higher temperatures under in vitro assay conditions. Overexpression of these proteins was found to impart substantial stress resilience to the transformed E. coli cells. These findings collectively suggest that GLYIII proteins constitute a key component of the abiotic stress response machinery in wild rice.

Oryza↗
PubMed2026

Advances in CRISPR Base Editing: From Molecular Evolution to Therapeutic Applications in Genomic Medicine.

CRISPR-Cas9 systems revolutionized gene editing, but inherent drawbacks, namely DNA double-strand breaks (DSBs) and the difficulty of achieving precise repairs (due to low HDR efficiency), led researchers to invent new, more accurate gene editing tools. Base editing represents a significant leap forward, enabling targeted single-nucleotide conversions directly on the DNA without DSBs or donor templates. The core technology involves fusing catalytically dead or nickase Cas proteins to DNA deaminase enzymes. Cytosine base editors (CBEs) convert C•G to T•A pairs, while adenine base editors (ABEs) change A•T to G•C. These editors exploit the deaminase function within the R-loop structure formed by Cas binding and co-opt endogenous DNA repair mechanisms for precision. While offering improved efficiency and editing precision, base editing faces persistent challenges, such as off-target effects, bystander edits, delivery and ethical concerns. Continuous engineering efforts have refined these tools, enhancing accuracy, expanding targetability and reducing unwanted edits. The base editing arsenal has also broadened to include C-to-G base editors (CGBEs), dual A&C editors and versions targeting organelles. Successful preclinical studies demonstrating the correction of mutations responsible for the disease have paved the way for clinical trials, which are now testing therapies for conditions like sickle cell disease, β-thalassaemia and hypercholesterolemia using various delivery systems. This review explores CRISPR base editing's origins, mechanisms of action, potential therapies and current restrictions, pointing to its broadening impact on medical genetics.

Humans↗
PubMed2026

Comparative Analysis of Chloroplast Genomes Reveals Molecular Evolution and Phylogenetic Relationships in Fraxinus (Fraxinus mandshurica).

Fraxinus mandshurica (Manchurian ash) is an ecologically and economically valuable hardwood tree native to Northeast Asia, yet its genomic resources remain limited. We assembled its complete chloroplast (cp) genome (155,559 bp) using hybrid PacBio and Illumina sequencing and performed comparative, phylogenetic, and evolutionary analyses. The cp genome exhibits a typical quadripartite structure encoding 132 gene copies, comprising 114 unique genes (80 protein-coding, 30 tRNA, and 4 rRNA genes), with 18 genes duplicated in the inverted repeat (IR) regions. Simple sequence repeat analysis revealed dominance of mononucleotide A/T repeats. Phylogenetic analysis of 53 complete cp genomes strongly supported the monophyly of Oleaceae and resolved F. mandshurica as sister to the North American F. nigra, consistent with previously proposed Miocene intercontinental dispersal scenarios between East Asia and North America. Most protein-coding genes were under strong purifying selection (Ka/Ks << 1), whereas petB, rpl2, and several ndh genes showed elevated Ka/Ks values that are suggestive of altered selective constraint but are based on very few substitutions and are therefore not, on their own, evidence of positive selection. Nucleotide diversity (Pi) analysis identified 15 hypervariable intergenic spacers (mean Pi = 0.067), among which trnM-CAU-rps14, ndhJ-ndhK, and petL-petG represent promising candidate barcode regions requiring further validation. This study provides a high-quality, fully annotated cp genome of F. mandshurica and a valuable genomic resource for future phylogenetic, population genetic, and conservation studies of this important genus.

Fraxinus↗
PubMed1992

Redesign of the substrate-binding site of hen egg white lysozyme based on the molecular evolution of C-type lysozymes.

On the basis of the molecular evolution of hen egg white, human, and turkey lysozymes, three replacements (Trp62 with Tyr, Asn37 with Gly, and Asp101 with Gly) were introduced into the active-site cleft of hen egg white lysozyme by site-directed mutagenesis. The replacement of Trp62 with Tyr led to enhanced bacteriolytic activity at pH 6.2 and a lower binding constant for chitotriose. The fluorescence spectral properties of this mutant hen egg white lysozyme were found to be similar to those of human lysozyme, which contains Tyr at position 62. The replacement of Asn37 with Gly had little effect on the enzymatic activity and binding constant for chitotriose. However, the combination of Asn37----Gly (N37G) replacement with Asp101----Gly (D101G) and Trp62----Tyr (W62Y) conversions enhanced bacteriolytic activity much more than each single mutation and restored hydrolytic activity toward glycol chitin. Consequently, the mutant lysozyme containing triple replacements (N37G, W62Y, and D101G) showed about 3-fold higher bacteriolytic activity than the wild-type hen lysozyme at pH 6.2, which is close to the optimum pH of the wild-type enzyme.

Acetylglucosamine↗
PubMed1992

Phylogenetic analysis of 48 papillomavirus types and 28 subtypes and variants: a showcase for the molecular evolution of DNA viruses.

Papillomaviruses are attractive models for studying the molecular evolution of DNA viruses because of the large number of isolates that exhibit genomic diversity and host species and tissue specificity. To examine their relationship, we selected two amino acid sequences, one of 52 residues within the early gene E1 and the other of 44 residues within the late gene L1, which allowed insertion- and deletion-free alignment of all accessible papillomavirus sequences. We constructed phylogenetic trees from the amino acid and corresponding nucleotide sequences from 28 published and 20 newly determined animal and human papillomavirus (HPV) genomic sequences by using distance matrix, maximum-likelihood, and parsimony methods. The trees agreed in all important topological aspects. One major branch with two clearly separated clusters contained 11 HPV types associated with epidermodysplasia verruciformis. A second major branch had all the papillomaviruses involved in genital neoplasia and, in distant relationship, the cutaneous papillomaviruses HPV type 2a (HPV-2a), HPV-3, and HPV-10 as well as the "butcher's" papillomavirus HPV-7 and two simian papillomaviruses. Four artiodactyl (even-toed hoofed mammal) papillomaviruses, the cottontail rabbit papillomavirus, and avian (chaffinch) papillomavirus type 1 formed a third major branch. Last, four papillomaviruses exhibited little affinity to any of these three branches; these were the cutaneous types HPV-1a, HPV-4, and HPV-41 and B-group bovine papillomavirus type 4. The phylogeny suggests that some branches of papillomavirus evolution are restricted to particular target tissues and that a general process of long-term papillomavirus-host coevolution has occurred. This latter hypothesis is still conjectural because of bias in the current data base for human types and the paucity of animal papillomavirus sequences. The comparison of evolutionary distances for the most closely related types with those of 28 subtypes and variants of HPV-2, HPV-5, HPV-6, HPV-16, and HPV-18 supports the type as a natural taxonomic unit, with subtypes and variants being expressions of minor intratype genomic diversity similar to that found in the natural populations of all biological species. An exception to this seems to be HPV-2c, which has an evolutionary distance from HPV-2a of the intertype magnitude and may eventually have to be regarded as a distinct type. We describe an experimental approach that estimates the taxonomic and phylogenetic positions of newly identified papillomaviruses without viral isolation and complete genomic sequencing.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗
PubMed1992

Comparative variation of morphological and molecular evolution through geologic time: 28S ribosomal RNA versus morphology in echinoids.

The comparatively good fossil record of post-Palaeozoic echinoids allows rates of morphological change to be estimated over the past 260 million years and compared with rates of molecular evolution. Parsimony analysis of morphological data, based predominantly on skeletal characteristics, and parsimony, distance and maximum likelihood analyses of molecular data, from the first 380 bases from the 5' end of the 28S rRNA molecule, for 10 species of echinoid produce congruent phylogenies. The molecular sequence chosen is demonstrably far from saturation and sister groups have divergence times ranging from about 15 to 260 Ma. Parsimony analysis allows the great majority of molecular and morphological apomorphies to be placed in one of 18 independent geological time intervals, providing a direct measure of rates of evolution for periods in the geological past. Because most molecular fixed point mutations in our sequences cannot be polarized unambiguously by outgroup comparison (making the outgroup states effectively random), distance and parsimony analyses both tend spuriously to root the echinoid tree on the longest internal branch. A topology identical to that derived from morphological data is, however, obtained using Maximum Likelihood and also parsimony analysis where outgroup rooting is restricted to more conserved regions. This is taken as the correct topology for assessing rates of evolution. Overall, both morphological and molecular changes show a moderately strong correlation with time elapsed, but a weaker correlation with one another. Statistically significant differences in evolutionary rate are found between some, but not all, pair-wise comparisons of sister lineages for both molecular and morphological data. The molecular clock rate for echinaceans is three times faster than that for cidaroids and irregular echinoids. Spearman's rank correlation test, which requires only relative magnitude of changes to be known, suggests that morphological change has a slightly better correlation with time than does molecular change, averaged over all ten species. However, when just echinaceans are considered an extremely good correlation is found between the number of molecular changes and time elapsed, whereas morphological change remains poorly correlated. Thus, molecular rates approximate to a clocklike model within restricted echinoid clades, but vary significantly between clades. Averaging results over all echinoids produces a correlation that is no better than the correlation between morphological change and time elapsed.

Animals↗
PubMed1992

Molecular evolution of alanine/glyoxylate aminotransferase 1 intracellular targeting. Analysis of the marmoset and rabbit genes.

In mammals, the subcellular distribution of alanine:glyoxylate aminotransferase 1 (AGT) is species dependent, with the proportion of AGT targeted to mitochondria varying between 0% and greater than 90%, the remainder being located in the peroxisome. In order to extend our studies on the molecular evolution of intracellular targeting of AGT, we have investigated the organization and expression of the AGT genes of rabbit, which has all of its AGT located in the peroxisome, and marmoset, which has approximately 50% of its AGT located in the peroxisome and 50% in the mitochondrion. Southern-blot analysis indicates that, in both of these species, AGT is encoded by a single-copy gene, as has previously been shown for human (all AGT in the peroxisome) and rat (50% AGT in the peroxisome and 50% in the mitochondrion). Comparison of the cDNA sequences encoding marmoset, rabbit, human and rat AGT, combined with transcript mapping and in vitro mitochondrial protein-import analysis, has provided a molecular explanation for the differential targeting of AGT in these species. As in the rat, marmoset AGT is synthesized in two forms, via the use of alternative transcription and translation-initiation sites. These two forms of AGT differ only in the presence or absence of a 22-amino-acid amino-terminal peptide, which acts as a cleavable mitochondrial-targeting sequence, directing the longer form of AGT to mitochondria. The shorter form of AGT, lacking the mitochondrial-targeting sequence, is presumed to be localized in the peroxisomes. In humans and rabbits, similar but distinct evolutionary mutational events within the AGT gene have resulted in exclusion of the region encoding the mitochondrial-targeting sequence from the open reading frame, explaining the exclusive peroxisomal localization of AGT in these species. We discuss the impact of these results on our understanding of both the evolution of species dependence of AGT subcellular distribution and the recent identification of amino acid changes in human AGT which result in mistargeting of this protein to mitochondria.

Alanine Transaminase↗
PubMedDate not supplied

[Molecular evolution of glycogen phosphorylase and aminotransferases of vertebrate muscle tissue].

Comparative biochemical studies on phosphorylase b, aspartate aminotransferase and alanine aminotransferase in muscles of various vertebrates (the lamprey Lampetra fluviatilis, dogfish Squalus acanthias, rays Dasyatis pastinaca and Raja clavata, teleosts Scorpaena porcus, Spicara smaris, Esox lucius, Tinca tinca, Abramis brama, Lucioperca lucioperca, Cyprinus carpio, Salmo ischchan, frog Rana temporaria, tortoise Testudo horsfieldi) revealed some peculiarties of their molecular evolution. It was shown that isoenzyme PH-II, which comprises in most on the investigated lower vertebrates the main bulk of phosphorylase b, disappears in evolution of the type. Isoenzyme PH-I which is found in fisches in small amounts, increases in evolution becoming the sole form of phosphorylase b in skeletal muscles of endothermic animals. Mitochondrial and cytoplasmic isoenzymes of aspartate aminotransferase were found in all the vertebrates studied. Cytoplasmic isoenzyme from ectothermic and endothermic animals does not differ significantly, whereas the mitochondrial one undergoes considerable changes in the evolution of vertebrates.

Alanine Transaminase↗
PubMed2026

Spatial proteomics reveals four-stage molecular evolution in cancer immunotherapy-related gastritis.

BACKGROUND: Immune checkpoint inhibitors (ICIs) have transformed cancer treatment, yet immune-related adverse events (irAEs) including immunotherapy-related gastritis (IRAEG) pose significant clinical challenges-often necessitating treatment interruption that may compromise antitumor efficacy. IRAEG presents with atypical symptoms, lacks specific biomarkers, and shows histopathological overlap with other forms of gastritis, complicating diagnosis and management. Despite increasing clinical recognition, a systematic understanding of spatial molecular alterations across the full disease course remains limited. Here, we used spatial proteomics to map the molecular landscape of IRAEG during disease progression and to define stage-specific patterns of molecular evolution relevant to cancer immunotherapy management. METHODS: We analyzed tissue samples from seven patients, including four non-immunotherapy-related gastritis controls and three cancer patients who developed IRAEG following ICI therapy for solid tumors, sampled longitudinally across four disease stages: baseline (G1), acute severe inflammation (G2), early recovery (G3), and complete recovery (G4). Using laser capture microdissection coupled with data-independent acquisition mass spectrometry, we profiled 177 spatially resolved gastric tissue regions. Multiplex immunohistochemistry and immunofluorescence characterized features of the immune microenvironment, while Gene Ontology, KEGG pathway analysis, Gene Set Variation Analysis, and xCell inference enabled functional, metabolic, and immune profiling. Key immune and NET-related findings were further validated by multiplex immunofluorescence in an independent, expanded cohort of IRAEG and non-immunotherapy-related gastritis samples. RESULTS: IRAEG was characterized by widespread HLA molecule activation and enhanced antigen processing, resembling the immune phenotype observed in organ transplant rejection. The acute G2 stage exhibited excessive neutrophil extracellular trap formation, profound metabolic suppression, and collapse of immune homeostasis-features that may inform early intervention strategies to preserve ICI treatment continuity. During early recovery (G3), inflammatory injury transitioned toward repair, marked by activation of fatty acid metabolism and PPAR signaling. Notably, even at complete clinical recovery (G4), more than 1,000 proteins remained differentially expressed, reflecting sustained enhancement of metabolic and immune functions and establishing a distinct molecular "memory" state with implications for ICI rechallenge decisions. CONCLUSIONS: These findings define four molecularly distinct stages of IRAEG progression and recovery. The stage-specific signatures identified here serve as candidate biomarkers for diagnosis, disease staging, and therapeutic response assessment, and may guide clinical decisions regarding irAE management, treatment modification, and safe ICI rechallenge to support continued antitumor therapy.

Humans↗
PubMed1992

The catalytic power of pyruvate decarboxylase. A stochastic model for the molecular evolution of enzymes.

Pyruvate decarboxylase (PDC) catalyzes the decarboxylation of pyruvate anion by a factor of around 10(12), compared with the non-enzymic decarboxylation by thiamine, under standard state conditions of 1 mM pyruvate and thiamine diphosphate (TDP), pH 6.2. Free-energy diagrams constructed on the basis of earlier measurements for the enzymic and non-enzymic reactions give some information on catalysis by PDC. PDC stabilizes the reactant state preceding TDP addition to pyruvate by 76 kJ mol-1 and the transition state for the addition by 83 kJ mol-1. PDC stabilizes the reactant state preceding decarboxylation (presumably alpha-lactyl-TDP) by 27 kJ mol-1 and the transition state for decarboxylation by 68 kJ mol-1. In addition, the free-energy diagrams reveal a leveling of reactant-state free energies in the enzymic reaction compared with the non-enzymic reaction, in that the former are nearly equal to each other. The enzyme-bound transition-state energies are similarly leveled. The energetic leveling of reactant states has been noted by Albery, Knowles and their coworkers in many enzymic reactions and termed 'matched internal thermodynamics.' They showed that the result would arise naturally (and inevitably) in the 'evolution to perfection' of enzymes, when the evolutionary process was treated by a deterministic model. The critical assumption of this model was the validity of a Marcus-type or Brønsted-type linear free-energy relationship between rate and equilibrium constants for reactions occurring wholly within enzyme complexes. Here a completely stochastic simulation of molecular evolution, with no deterministic assumptions, is shown to reproduce both 'matched internal thermodynamics' and the 'matched internal kinetics' or leveling of transition-state energies noted here. The Albery-Knowles result is thus more general than might have been supposed.

Biological Evolution↗
PubMed1991

Molecular evolution of hemagglutinin genes of H1N1 swine and human influenza A viruses.

The hemagglutinin (HA) genes of influenza type A (H1N1) viruses isolated from swine were cloned into plasmid vectors and their nucleotide sequences were determined. A phylogenetic tree for the HA genes of swine and human influenza viruses was constructed by the neighbor-joining method. It showed that the divergence between swine and human HA genes might have occurred around 1905. The estimated rates of synonymous (silent) substitutions for swine and human influenza viruses were almost the same. For both viruses, the rate of synonymous substitution was much higher than that of nonsynonymous (amino acid altering) substitution. It is the case even for only the antigenic sites of the HA. This feature is consistent with the neutral theory of molecular evolution. The rate of nonsynonymous substitution for human influenza viruses was three times the rate for swine influenza viruses. In particular, nonsynonymous substitutions at antigenic sites occurred less frequently in swine than in humans. The difference in the rate of nonsynonymous substitution between swine and human influenza viruses can be explained by the different degrees of functional constraint operating on the amino acid sequence of the HA in both hosts.

Amino Acid Sequence↗
PubMed1992

Characterization of two members (CST4 and CST5) of the cystatin gene family and molecular evolution of cystatin genes.

Two members (CST4 and CST5) of the cystatin gene family have been characterized partially by DNA analysis. The CST4 clone contained the gene coding for the precursor form(141 amino acids) of cystatin S, and its exon-intron organization is the same as that of other members (the cystatin SN gene at the CST1 locus, the cystatin SA gene at the CST2 locus, the cystatin C gene at the CST3 locus and a cystatin pseudogene at the CSTP1 locus). The second cystatin pseudogene was elucidated in the clone, CST5, and it was assigned to the CSTP2 locus. Alignment of DNA sequences of cystatin genes with other genes suggested that the genes for cystatins, kininogens, and Bowman-Birk type inhibitors have evolved from an ancient ribonuclease-like gene.

Amino Acid Sequence↗
PubMed1991

Molecular evolution in hypotrichous ciliates: sequence of the small subunit ribosomal RNA genes from Onychodromus quadricornutus and Oxytricha granulifera (Oxytrichidae, Hypotrichida, Ciliophora).

The small subunit ribosomal RNA (16S-like rRNA) coding regions of the hypotrichous ciliates Onychodromus quadricornutus and Oxytricha granulifera were amplified using polymerase chain reaction techniques. Complete sequences were determined for the amplified genes and compared to those of other ciliated protozoa. In phylogenetic trees inferred using distance matrix methods oxytrichids are not seen as a cohesive phylogenetic group. Oxytricha nova is most closely related to Stylonychia pustulata in a lineage that also includes O. quadricornutus. This phylogeny contradicts phylogenetic schemes in which Onychodromus is considered to be a primitive hypotrichous ciliate and suggests that O. nova was misidentified as members of the genus Oxytricha.

Animals↗
PubMed2025

Molecular Evolution and Zoonotic Potential of Muju Virus (Orthohantavirus puumalaense) in Craseomys regulus, Republic of Korea.

Orthohantavirus puumalaense causes hemorrhagic fever with renal syndrome in Europe, with Puumala virus (PUUV) as its primary representative. Muju virus (MUJV), harbored by Craseomys regulus, an Arvicolinae rodent species endemic to the Republic of Korea (ROK), is also a genotype of O. puumalaense. However, their genomic diversity and zoonotic potential remain largely unknown. To investigate their prevalence, 185 voles were collected from 23 regions of the ROK between 2012 and 2023. Serological assays detected anti-PUUV immunoglobulin G antibodies in five samples (3.1%), whereas reverse-transcription polymerase chain reaction confirmed MUJV RNA in identical specimens (2.7%). Amplicon-based nanopore sequencing facilitates near-complete genome recovery, enabling high-resolution comparative analysis. Phylogenetic analysis revealed distinct genetic lineages in Gangwon and Jeollabuk Provinces. Evolutionary rate estimates indicated greater sequence divergence in the S and L segments than in the M segment. A zoonotic risk assessment revealed that most MUJV variants exhibited moderate-to-high spillover potential. The molecular detection of MUJV in Cheorwon, Gangwon Province, expands its known geographic range and provides the first molecular evidence of MUJV circulation in this region. These findings highlight the need for continued surveillance and seroprevalence studies of MUJV to assess its potential for human exposure and public health relevance in the ROK.

Animals↗
PubMed1992

Mo-MuLV nucleotide sequence exhibits three levels of oligomeric repetitions, suggesting a stepwise molecular evolution.

An exhaustive computer-assisted analysis of the Moloney murine leukemia virus nucleotide sequence shows numerous deviations in the oligomeric distribution, suggesting three overlapping levels of a stepwise duplicative evolution. (1) The sequence fits the universal rule of TG/CT excess which has been proposed as the construction principle of all sequences, and maintains some degree of symmetry between the two complementary strands. (2) Oligomeric repeating units share a core consensus regularly scattered throughout the sequence. This consensus is not merely predictable from the doublet frequencies and codon usage, but could correspond to an intermediary stage in a so-called periodic-to-chaotic transition. (3) Probable stepwise local duplications could be accounted for by slippagelike mechanisms. Comparison with the human spumaretrovirus (HSRV) shows similar segments in the overrepresented oligomers of the two sequences. The intermediary stage of transition oligomeric repeating units is not so clearly suggested in HSRV, perhaps because of numerous stepwise local duplications. In any case, a common evolutionary origin for the two viruses is not ruled out.

Base Sequence↗