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Results for “nucleotide polymorphism patterns”

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PubMed1994

Analysis of the tumor suppressor gene p53 in xeroderma pigmentosum fibroblasts.

Genetic risk factor(s) for skin cancers have been described in patients with xeroderma pigmentosum (XP). The tumor suppressor gene, p53, is one of the most frequently mutated genes found in human tumors. To evaluate the role of XP-related genetic defects in the p53 gene, skin fibroblast cell lines derived from XP donors were analysed for mutations in exons 5-9 (the regions of gene highly susceptible for mutations) by single-strand conformation polymorphism (SSCP) and nucleotide sequencing. Of the five XP-derived fibroblasts (complementation group A) and two control fibroblast cell lines, only one XP cell line showed an aberrant SSCP banding pattern in the region of the p53 gene (comprising the 7th exon and neighbouring intronic sequences). Nucleotide sequencing of this region confirmed a mutation in the 7th intron adjacent to the 7th exon, which did not affect the RNA splice site. These results suggest that constitutional/germ-line mutations in the p53 gene may not play a role in the occurrence of skin carcinomas in XP patients.

Base Sequence↗

PubMed2026

A comprehensive survey of genetic variants in neuroblastoma.

BACKGROUND: Neuroblastoma (NB) is the most common extracranial solid tumor in children and is characterized by marked clinical and molecular heterogeneity. Genomic alterations play a critical role in NB pathogenesis; however, population-specific mutational features remain insufficiently characterized, particularly among Chinese patients. METHODS: Whole-exome sequencing (WES) was performed on tumor, para-tumor, and matched peripheral blood samples from nine pathologically confirmed Chinese patients with NB. Somatic variant profiles were compared with four publicly available NB datasets from cBioPortal, published in 2012, 2013, 2015, and 2023. Mutational patterns, recurrently altered genes, and Gene Ontology (GO) enrichment were analyzed using R version 4.3.2 and clusterProfiler version 4.10.0. RESULTS: A total of 77 missense variants were identified in our cohort. Single-nucleotide polymorphisms (SNPs) represented the predominant variant type, and C > T substitutions were the most frequent nucleotide change. MAP1A variants, comprising two missense variants in one patient, and RBM33 variants, comprising two distinct variants in two patients, were detected in our cohort and, to the best of our knowledge, have not been previously reported in NB, although their frequencies were low. No MYCN amplification or variants in ALK, ATRX, or DAXX were detected. Comparative analysis with the cBioPortal datasets revealed no somatic variants universally shared across all cohorts. In addition, high-risk patients exhibited distinct mutational patterns, with enrichment of the Gene Ontology term "collagen-containing extracellular matrix." CONCLUSIONS: These findings highlight the molecular diversity of NB and suggest the presence of potential population-specific genetic features in Chinese patients. The low-frequency MAP1A and RBM33 variants identified in this cohort warrant further validation in larger, independent cohorts. Moreover, the enrichment of extracellular matrix-related pathways in high-risk NB supports further investigation of tumor-microenvironment interactions as potential therapeutic targets.

Extracellular matrix↗

PubMed1992

A new polymorphism in exon 11 of the LDL receptor gene in healthy people and in familial hypercholesterolemia subjects.

We have screened exon 11 of the low density lipoprotein receptor (LDLR) gene from familial hypercholesterolemia (FH) heterozygotes for point mutations by using analysis of single strand conformation polymorphisms (SSCP). A variant pattern was observed in three out of 39 subjects. By DNA sequencing, this variant pattern was found to be due to a C-->T transition at nucleotide 1617 that affects the third base of codon 518. A PCR method was developed to screen FH heterozygotes and normal subjects for this mutation. The gene frequencies in FH heterozygotes and normal subjects were 4% and 4.5%, respectively. Thus, the mutation cannot be in linkage disequilibrium with a mutation that causes FH. Rather, the mutation may be a useful genetic marker at the LDLR locus. Haplotype analysis at the LDLR locus in two FH families where the proband possessed the mutation revealed that the mutation was on two different haplotypes. This finding is consistent with the mutation occurring at a mutational hot spot.

Base Sequence↗

PubMed1991

Inferring the evolutionary histories of the Adh and Adh-dup loci in Drosophila melanogaster from patterns of polymorphism and divergence.

The DNA sequences of 11 Drosophila melanogaster lines are compared across three contiguous regions, the Adh and Adh-dup loci and a noncoding 5' flanking region of Adh. Ninety-eight of approximately 4750 sites are segregating in the sample, 36 in the 5' flanking region, 38 in Adh and 24 in Adh-dup. Several methods are presented to test whether the patterns and levels of polymorphism are consistent with neutral molecular evolution. The analysis of within- and between-species polymorphism indicates that the region is evolving in a nonneutral and complex fashion. A graphical analysis of the data provides support for a hypothesized balanced polymorphism at or near position 1490, site of the amino acid replacement difference between Adhf and Adhs. The Adh-dup locus is less polymorphic than Adh and all 24 of its polymorphisms occur at low frequency--suggestive of a recent selective substitution in the Adh-dup region. Adhs alleles form two distinct evolutionary lineages that differ one from another at a total of nineteen sites in the Adh and Adh-dup loci. The polymorphisms are in complete linkage disequilibrium. A recombination experiment failed to find evidence for recombination suppression between the two allelic classes. Two hypotheses are presented to account for the widespread distribution of the two divergent lineages in natural populations. Natural selection appears to have played an important role in governing the overall patterns of nucleotide variation across the two-gene region.

Alcohol Dehydrogenase↗

PubMed1998

High frequency of polymorphism but no mutations found in the GLUT1 glucose transporter gene in NIDDM and familial obesity by SSCP analysis.

To evaluate whether a structural defect in the human glucose transporter gene GLUT1 could be involved in the aetiology of insulin resistance, a key factor of non-insulin-dependent diabetes mellitus (NIDDM) and obesity, we performed single-strand conformation polymorphism (SSCP) analysis in 40 subjects (20 NIDDM patients and 20 subjects with familial obesity). The GLUT1 gene, which is involved in basal glucose transport in most tissues, consists of ten exons and encodes a 492 amino acid protein. Population studies have shown a strong association between the X1 allele of an XbaI restriction fragment length polymorphism of the GLUT1 gene and NIDDM. We therefore performed SSCP analysis in NIDDM subjects known to carry at least one X1 allele. Variant SSCP patterns were detected in exons 2, 4, 5 and 9. Sequence analysis of the SSCP variants revealed the presence, in all exons examined, of silent mutations consisting of single-nucleotide substitutions with no amino acid changes. Both NIDDM and obese patients showed a high frequency of polymorphism in the sequence (50% and 35%, respectively). We conclude that the GLUT1 gene is unlikely to play a role in the aetiology of NIDDM and obesity. However, the strong association between the GLUT1 gene and NIDDM, together with the recent family studies showing linkage between chromosome 1p and NIDDM warrant further studies on this chromosomal region.

Adult↗

PubMed2000

Differentiation of Castor fiber and Castor Canadensis by noninvasive molecular methods.

The aim of the study was to develop a simple and reliable method for differentiation of the two phenotypic, very similar Eurasian and North American beavers. Hair bulbs were plucked as tissue samples from the fur of living animals. The mitochondrial cytochrome b locus was amplified by polymerase chain reaction and sequenced. The fragments of the two species differed at 44/41 nucleotide sites. RsaI recognised two mutations, resulting in a restriction fragment length polymorphism that seems to be species specific, as could be revealed by the banding pattern. Zoo Biol 19:511-515, 2000. Copyright 2000 Wiley-Liss, Inc.

Journal Article↗

PubMed1996

Sequencing and detection of polymorphisms in the 5' end of the human endogenous retroviral element, HRES-1.

Fragments of the 5' long terminal repeat (LTR) of the human endogenous retroviral element, HRES-1, were amplified. Single strand conformation analysis of these fragments in combination with sequencing revealed two polymorphic nucleotides, namely a HindIII and an Eco571 polymorphic site. Moreover, a number of differences from the previously published HRES-1 LTR sequence were detected. The linkage pattern of the two polymorphisms suggested the existence of three allelic forms of HRES-1. The frequencies of the genotypes and alleles of HRES-1 were determined in 158 individuals. The detection of HRES-1 markers may be useful to study associations between this endogenous retrovirus and various diseases.

Base Sequence↗

PubMed1999

A novel haplotype of the endogenous retrovirus, HRES-1, in patients with multiple sclerosis and healthy individuals.

In this study we searched for genetic variation in a segment of the human endogenous retrovirus, HRES-1, which encodes a potential autoantigen of 28 kDa. The purpose was to further investigate a possible association between this endogenous retrovirus and multiple sclerosis (MS). Fragments amplified from the HRES-1 region in question were subjected to single strand conformational analysis (SSCP analysis) and sequencing if the SSCP migration pattern suggested presence of polymorphisms. Using this approach a synonymous G --> C substitution, creating an NciI site, was found. Our sequence data also revealed an additional nucleotide in the region encoding the 28-kDa protein, i.e. a nucleotide not present in the first published sequence. This finding has implications for future studies of the 28-kDa HRES-1 protein since the additional nucleotide changes the reading frame of this protein. The detection of the Nci polymorphism allowed us to define a novel haplotype of HRES-1 distinct from the three previously known HRES-1 haplotypes. On comparison of the distribution of these four haplotypes in MS patients and healthy individuals we found a statistically significant difference (P = 0.03) but the contribution from the novel haplotype to this was modest.

Alleles↗

PubMed1999

High and intermediate resolution DNA typing systems for class I HLA-A, B, C genes by hybridization with sequence-specific oligonucleotide probes (SSOP).

DNA typing systems for alleles of the HLA class I loci A, B, C at intermediate (IR) and high resolution (HR) levels were developed. The approaches combine locus-specific amplification of genomic DNA by the polymerase chain reaction (PCR) and hybridization with sequence-specific oligonucleotide probes (SSOP). The SSOP were designed to match nucleotide sequences at all polymorphic sites of exons 2 and 3 at these loci. Alleles and genotypes for these loci are assigned by their unique hybridization patterns. Some genotypes with particular allele combinations resulted in the same hybridization pattern. These genotype ambiguities were resolved by performing additional group-specific amplifications with appropriate GSA primers and hybridization with informative SSOP. At intermediate resolution level, many groups of alleles of HLA-A and B with the same serologic equivalence resulted in the same hybridization pattern. Both HR and IR typing approaches required the design, validation and testing of locus- and group-specific primers and sequence-specific oligonucleotide probes (SSOP). Single locus-specific amplification and hybridization with sets of 67 SSOP for HLA-A, 99 for HLA-B and 57 for HLA-C allowed us to identify unequivocally the majority of A, B, C alleles at HR level. To resolve ambiguous genotypes at HLA-B, we performed 4 GSA with 5' primers at codon 45-46 and hybridization with selected sets of SSOP. About 22,415 high resolution typing results were obtained (4,953A, 6,621B, 10,841C). In these samples, 63 HLA-A, 170 HLA-B and 40 HLA-C alleles were observed. In the course of these studies, more than 30 new alleles have been identified. In IR testing, sets of 39 SSOP for HLA-A typing and 59 SSOP for HLA-B typing allowed us to obtain maximal resolution of the majority of common genotypes. To achieve IR level, the majority of SSOP selected were those that span codons encoding amino acid residues located in the alpha helical segments of the class I molecules. A total of 50,522 samples were typed for HLA-A and B at IR level. Approximately 2.0% of them carried ambiguous genotypes associated with alternative switches of Bw4/w6 related sequences. All these ambiguities were resolved by Bw4/Bw6 GSA by 2 primer pairs (77N-IALR-83/3B.1; 77S-DLRG-83/3B.1) and hybridization with 9 selected SSOP Testing was performed by individual hybridization of replicate dot blot membranes with the SSOP of the corresponding set. The approach was robust and cost-effective in large-scale HLA class I molecular typing. The resolution provided by HLA-A, B IR reached serologic split-level or higher. The description of primers and probes for HLA class I typing may be utilized as starting elements for development of second generation methods with a more rapid turn around time.

DNA↗

PubMed1995

Multiple glucose 6-phosphate dehydrogenase-deficient variants correlate with malaria endemicity in the Vanuatu archipelago (southwestern Pacific).

In studying the relationship between genetic abnormalities of red blood cells and malaria endemicity in the Vanuatu archipelago in the southwestern Pacific, we have found that of 1,442 males tested, 98 (6.8%) were G6PD deficient. The prevalence of GdPD deficiency varied widely (0%-39%), both from one island to another and in different parts of the same island, and generally correlated positively with the degree of malaria transmission. The properties of G6PD from GdPD-deficient subjects were analyzed in a subset of 53 samples. In all cases the residual red-blood-cell activity was < 10%. There were three phenotypic patterns. PCR amplification and sequencing of the entire coding region of the G6PD gene showed that the first of these patterns corresponded to G6PD Union (nucleotide 1360C-->T; amino acid 454Arg-->Cys), previously encountered elsewhere. Analysis of samples exhibiting the second pattern revealed two new mutants: G6PD Vanua Lava (nucleotide 383T-->C; amino acid 128Leu-->Pro) and G6PD Namoru (nucleotide 208T-->C; amino acid 70Tyr-->His); in three samples, the underlying mutation has not yet been identified. Analysis of the sample exhibiting the third pattern revealed another new mutant: G6PD Naone (nucleotide 497G-->A; amino acid 166Arg-->His). Of the four mutations, G6PD Union and G6PD Vanua Lava have a polymorphic frequency in more than one island; and G6PD Vanua Lava has also been detected in a sample from Papua New Guinea. G6PD deficiency is of clinical importance in Vanuatu because it is a cause of neonatal jaundice and is responsible for numerous episodes of drug-induced acute hemolytic anemia.

Adolescent↗

PubMed2001

Genome and genetic resources from the Cancer Genome Anatomy Project.

The Cancer Genome Anatomy Project (CGAP) is a collaborative network of cancer researchers with a common goal: to decipher the genetic changes that occur during cancer formation and progression. The project brings together several recent technologies capable of high-throughput analysis to help achieve this goal. Automated sequencing of cDNA libraries is a primary focus and is geared towards providing a comprehensive and annotated set of human and mouse transcribed sequences. This effort includes full-length transcript sequence generated by CGAP's new Mammalian Gene Collection initiative. Single nucleotide polymorphisms (SNPs) within human gene sequences (Genetic Annotation Initiative) and chromosomal rearrangements within cancer cells (Cancer Chromosome Aberration Project) are also being cataloged as part of CGAP. Finally, to help determine gene expression patterns related to cancer, CGAP provides a quantitative catalog of data through its SAGEmap initiative. The genome and genetic analysis tools listed in this review are all freely distributed by CGAP (http://cgap.nci.nih.gov/) without restriction.

Animals↗

PubMed1997

The Arg633His substitution responsible for the private platelet antigen Gro(a) unravelled by SSCP analysis and direct sequencing.

We have previously described the private or family platelet antigen, Gro(a), which was identified in a case of neonatal alloimmune thrombocytopenia. The Gro(a) antigen was found to be located on the GP IIIa (beta3) subunit of the GP IIb/IIIa complex, the most prominent fibrinogen receptor of platelets. Initial experiments to characterize the Gro(a) antigen at the molecular genetic level were unsuccessful. We therefore decided to use a different strategy to unravel the molecular basis of this antigen. Platelet GP IIIa mRNA of a Gro(a+) and a Gro(a-) donor was amplified with suitable primers in a reverse transcriptase-polymerase chain reaction (RT-PCR) and subjected to single-strand conformational polymorphism (SSCP) analysis. Three regions of the amplified GP IIIa cDNA derived from the Gro(a+) donor showed a different SSCP pattern when compared to that of the Gro(a-) donor. Direct nucleotide sequence analysis of these three segments revealed that two of them contained silent substitutions, A1163C, A1553G and G1565A. The first and the latter changes were described previously. In the third segment a G1996A mutation was found, predicting an arginine --> histidine substitution at position 633 of the mature glycoprotein. PCR-ASRA (allele-specific restriction enzyme analysis) performed on cDNA as well as on genomic DNA with the restriction enzyme MaeIII showed that the His633 form of GPIIIa is restricted to the Gro(a+) phenotype. The observed mutation is three amino acids upstream of the mutation underlying the HPA-8/Sr system (Arg636Cys), suggesting this region of GP IIIa to be susceptible for mutations. Moreover, the presence of a silent mutation and two low-frequency forms of the silent polymorphisms strongly suggests that the G1996A mutation did not occur in a direct ancestral allele.

Antibodies, Monoclonal↗

PubMed1997

Balancing selection on electrophoretic variation of phosphoglucose isomerase in two species of field cricket: Gryllus veletis and G. offnsylvanicus.

Two species of crickets, Gryllus veletis and G. pennsylvanicus, share six electrophoretic mobility classes for the enzyme phosphoglucose isomerase (PGI), despite evidence from other genetic markers that the two species are not closely related within eastern North American field crickets. Moreover, the frequencies of the two most common PGI electrophoretic classes (PGI-100 and PGI-65) covary in sympatric populations of these species in the eastern United States, suggesting that PGI may be subject to trans-specific balancing selection. To determine the molecular basis of the electrophoretic variation, we characterized the DNA sequence of the Pgi gene from 29 crickets (15 G. veletis and 14 G. pennsylvanicus). Amino acid substitutions that distinguish the electrophoretic classes are not the same in the two species, and there is no evidence that specific replacement substitutions represent trans-specific polymorphism. In particular, the amino acids that diagnose the PGI-65 allele relative to the PGI-100 allele differ both between G. veletis and G. pennsylvanicus and within G. pennsylvanicus. The heterogeneity among electrophoretic classes that covary in sympatric populations coupled with analysis of patterns of nucleotide variation suggest that Pgi is not evolving neutrally. Instead, the data are consistent with balancing selection operating on an emergent property of the PGI protein.

Animals↗

PubMed2000

Development of a PCR-SSOP approach capable of defining the natural killer cell inhibitory receptor (KIR) gene sequence repertoires.

A molecular typing method based on polymerase chain reaction (PCR) amplification of three different target domains (immunoglobulin domains 1 and 3, and the transmembrane-cytoplasmic domain), followed by hybridisation with 26 digoxigenin-labelled sequence-specific oligonucleotide probes (SSOP) has been established for the polymorphic killer inhibitory receptor (KIR) genes. In addition to identifying the 12 KIR subfamilies, our PCR-SSOP typing approach could also distinguish the putative alleles, NKB1 and NKAT3, that comprise the KIR3DL1 subfamily. Ninety unrelated blood donors and 13 families (52 individuals), including both parents, were subjected to our KIR PCR-SSOP typing approach. All 12 KIR subfamilies, including a 2DS5 variant sequence, were present in the 90 individuals and displayed varied phenotype frequencies: 2DL1 (0.96), 2DL2 (0.31), 2DL3 (0.95), 2DS1 (0.56) 2DS2 (0.51), 2DS3 (0.27), 2DS4 (0.96), 2DS5v (0.35), 3DS1 (0.47), 3DL1 (0.96), 3DL2 (1.0) and 2DL4 (1.0). A total of 23 different KIR phenotypes were defined in this study, and 10 of these were only found on one occasion in one individual, indicating considerable diversity in the KIR phenotype profiles within the Irish population. Most individuals (93%) possessed the complement of inhibitory KIR specificities for the three well-defined HLA-B and -C ligands. An unusual probe pattern for 3DS1 was observed in 3 individuals indicating a variant 3DS1 gene sequence with changes at nucleotide positions 1185-1186, within the cytoplasmic domain. Sequencing analysis revealed a new single nucleotide polymorphism in exon 3 of 3DL1 NKB1(195, G-A) and a 22-bp deletion polymorphism in exon 5 of 2DS4 (nucleotides 777-798 deleted). A number of strong KIR associations were observed, namely 2DL1 with 2DL3, 2DS4 with 3DL1, 2DL2 with 2DS1/2DS2/2DS3, 2DS1 with 2DS3/2DS5v/3DS1, 2DS2 with 2DS3 and 2DS5v with 3DS1. Analysis of the KIR segregation observed in the 13 families confirmed these strong associations and permitted the definition of a number of partial KIR haplotypes, e.g. 2DL2-2DS1-2DS2-2DS3-3DL1. The segregation analysis concluded that at least 3 distinct gene loci encode 2DL1-4 and at least 4 gene loci encode the non-inhibitory KIR2DS1-2DS5. In the case of 3DL1-2 and 3DS1, our data suggests 3 gene loci, one for each subfamily.

Humans↗

PubMed2000

Comparison of protein A gene sequencing with pulsed-field gel electrophoresis and epidemiologic data for molecular typing of methicillin-resistant Staphylococcus aureus.

The epidemiologic relatedness of methicillin-resistant Staphylococcus aureus (MRSA) isolates is currently determined by analysis of chromosomal DNA restriction patterns by pulsed-field gel electrophoresis (PFGE). We have evaluated an alternative typing system (MicroSeq StaphTrack Kit; Perkin-Elmer Biosystems) based on the sequence analysis of the chromosomally encoded polymorphic repeat X region of the S. aureus protein A (spa) gene. A total of 69 clinical MRSA isolates were divided into 18 groups according to the number and nucleotide sequences of the spa repeats. Molecular typing results obtained both by spa sequencing and from the PFGE patterns were concordant except for one group, which contained 20 isolates recovered over a 2-year period from hospitalized patients at the Mayo Clinic. Although the spa typing patterns were indistinguishable for those isolates, PFGE analysis yielded seven related but distinguishable patterns. Further coagulase gene sequence analysis subtyped those 20 strains into four groups which followed distinct temporal and geographic distributions. During a 2-year epidemic period there were up to 7 fragment changes in PFGE patterns among epidemiologically related isolates, suggesting that PFGE may be unsuitable for long-term typing of strains involved in epidemics. Although more limited than PFGE in discriminatory power, spa sequencing analysis could be used as a screening method for typing of MRSA strains because of the shorter turnaround time, ease of use, and the inherent advantages of sequence analysis, storage, and sharing of information.

Animals↗

PubMed1996

Ancestral major histocompatibility complex DRB genes beget conserved patterns of localized polymorphisms.

Genes within the major histocompatibility complex (MHC) are characterized by extensive polymorphism within species and also by a remarkable conservation of contemporary human allelic sequences in evolutionarily distant primates. Mechanisms proposed to account for strict nucleotide conservation in the context of highly variable genes include the suggestion that intergenic exchange generates repeated sets of MHC DRB polymorphisms [Gyllensten, U. B., Sundvall, M. & Erlich, H. A. (1991) Proc. Natl. Acad. Sci. USA 88, 3686-3690; Lundberg, A. S. & McDevitt, H. 0. (1992) Proc. Natl. Acad. Sci. USA 89, 6545-6549]. We analyzed over 50 primate MHC DRB sequences, and identified nucleotide elements within macaque and baboon DRB6-like sequences with deletions corresponding to specific exon 2 hypervariable regions, which encode a discrete alpha helical segment of the MHC antigen combining site. This precisely localized deletion provides direct evidence implicating segmental exchange of MHC-encoded DRB gene fragments as one of the evolutionary mechanisms both generating and maintaining MHC diversity. Intergenic exchange at this site may be fundamental to the diversification of immune protection in populations by permitting alteration in the specificity of the MHC that determines the repertoire of antigens bound.

Animals↗

PubMed1995

Characterisation of a novel minisatellite that provides multiple splice donor sites in an interferon-induced transcript.

Nucleotide sequence features of the human interferon-inducible gene 6-16 are described and include, within a CpG island, a partially expressed minisatellite consisting of 26 tandemly repeated dodecanucleotides. The repeat unit consensus sequence (CAGGTAAGGGTG) is similar to the mammalian splice donor consensus sequence [(A/C)AGGT(A/G)AGT]. The splice donor site of exon 2, as determined previously, forms part of the most upstream of the repeat units. We show that the two neighbouring repeat units also provide functional splice donor sites effectively extending exon 2 by 12 or 24 nt and inserting four or eight amino acids respectively into the predicted gene product. A similar pattern of differently spliced transcripts is detected in several human cell types. Both the number of repeat units per allele and the nucleotide sequence itself show limited polymorphism within the human population. Similar minisatellites from nonhuman primates are described and also appear to modulate splicing of a 6-16 transcript. The 6-16 minisatellite is therefore an example of tandemly repeated DNA that has a role in gene expression and may provide a useful in vivo system for the analysis of 5' splice site choice and minisatellite biology.

Amino Acid Sequence↗

PubMed1995

Interchromosomal exchange of genetic information between gene arrangements on the third chromosome of Drosophila pseudoobscura.

During the last 60 years, the inversion polymorphism on the third chromosome of Drosophila pseudoobscura has become a case study of the evolution of linked blocks of genes, isolated from each other by the suppression of recombination in heterozygotes for different inversions. Due to its location within inverted regions in most gene arrangements, the amylase (Amy) gene region can be used to elucidate the molecular pattern of evolution in these inversions. We studied this region in the Tree Line phylad of gene arrangements, with regard to both restriction site polymorphisms (RSP) and nucleotide sequences. The analysis of restriction maps, encompassing 26 kb, corroborates the cytogenetic phylogeny established on the basis of inversion breakpoints. However, we found that the 2.7 kb of nucleotide sequences of the AmyI gene are identical in both Estes Park and Hidalgo arrangements, despite the fact that these inversions arose independently from Tree Line. These contrasting results suggest that a homogenizing force, most likely gene conversion, is able to bring about localized exchanges between otherwise isolated gene arrangements.

Amylases↗