共查询到20条相似文献,搜索用时 31 毫秒
1.
Retroprocessed pseudogenes, calmodulin II (ψ1, ψ2, and ψ3 CALMII), ψα-tubulin, π-glutathione S-transferase (ψπ-GST) from rat, lactic acid dehydrogenase (ψ LDH) from mouse, and heat shock protein 60 chaperonin (ψ HSP60)
from Chinese hamster, were examined for their presence in these species by polymerase chain reaction (PCR). Pseudogenes of
these murine rodents were detected by PCR only in those species in which the genes were originally identified, suggesting
that the selected pseudogene of one species arose too recently to be detected in the genomes of the other rodent species.
The calculated ages of the rodent pseudogenes ranged from 1.7 Myr (ψα-tubulin) to 7.5 Myr (ψ3 CALMII) when employing a homologous functional gene of the taxon as a reference in the relative rate test with the mouse
or rat as the outgroup. Given the high rate of divergence of the genes of rodents relative to other species, selection of
an outgroup with similar mutation rates seems warranted. To justify further the conclusion that the selected pseudogenes were
indeed retroprocessed after these three taxa diverged, the presence of the pseudogenes in the genome of different rat species
was examined. The existence of ψ3 CALMII and ψα-tubulin pseudogenes of Rattus norvegicus among species belonging to Rattus sensu stricto is evidence for the common ancestry of this group.
Received: 23 May 2001 / Accepted: 31 May 2001 相似文献
2.
Keravala A Groth AC Jarrahian S Thyagarajan B Hoyt JJ Kirby PJ Calos MP 《Molecular genetics and genomics : MGG》2006,276(2):135-146
This study evaluated the ability of five serine phage integrases, from phages A118, U153, Bxb1, φFC1, and φRV1, to mediate recombination in mammalian cells. Two types of recombination were investigated, including the ability of an integrase to mediate recombination between its own phage att sites in the context of a mammalian cell and the ability of an integrase to perform genomic integration pairing a phage att site with an endogenous mammalian sequence. We demonstrated that the A118 integrase mediated precise intra-molecular recombination of a plasmid containing its attB and attP sites at a frequency of ∼ 50% in human cells. The closely related U153 integrase also performed efficient recombination in human cells on a plasmid containing the attB and attP sites of A118. The integrases from phages Bxb1, φFC1, and φRV1 carried out such recombination at their attB and attP sites at frequencies ranging from 11 to 75%. Furthermore, the A118 integrase mediated recombination between its attP site on a plasmid and pseudo attB sites in the human genome, i.e. native sequences with partial identity to attB. Fifteen such A118 pseudo att sites were analyzed, and a consensus recognition site was identified. The other integrases did not mediate integration at genomic sequences at a frequency above background. These site-specific integrases represent valuable new tools for manipulating eukaryotic genomes. 相似文献
3.
Artificial recombinants can be generated during PCR when more than two genetically distinct templates coexist in a single PCR reaction. These recombinant amplicons can lead to the false interpretation of genetic diversity and incorrect identification of biological phenotypes that do not exist in vivo. We investigated how recombination between 2 or 35 genetically distinct HIV-1 genomes was affected by different PCR conditions using the parallel allele-specific sequencing (PASS) assay and the next generation sequencing method. In a standard PCR condition, about 40% of amplicons in a PCR reaction were recombinants. The high recombination frequency could be significantly reduced if the number of amplicons in a PCR reaction was below a threshold of 1013–1014 using low thermal cycles, fewer input templates, and longer extension time. Heteroduplexes (each DNA strand from a distinct template) were present at a large proportion in the PCR products when more thermal cycles, more templates, and shorter extension time were used. Importantly, the majority of recombinants were identified in heteroduplexes, indicating that the recombinants were mainly generated through heteroduplexes. Since prematurely terminated extension fragments can form heteroduplexes by annealing to different templates during PCR amplification, recombination has a better chance to occur with samples containing different genomes when the number of amplicons accumulate over the threshold. New technologies are warranted to accurately characterize complex quasispecies gene populations. 相似文献
4.
Short Inverted-Repeat Transposable Elements in Teleost Fish and Implications for a Mechanism of Their Amplification 总被引:7,自引:0,他引:7
Zsuzsanna Izsvák Zoltán Ivics Nobuyoshi Shimoda Deanna Mohn Hitoshi Okamoto Perry B. Hackett 《Journal of molecular evolution》1999,48(1):13-21
Angel is the first miniature inverted-repeat transposable element (MITE) isolated from fish. Angel elements are imperfect palindromes with the potential to form stem-loop structures in vitro. Despite sequence divergence
of elements of up to 55% within and between species, their inverted repeat structures have been maintained, implying functional
importance. We estimate that there are about 103–104
Angels scattered throughout the zebrafish genome, evidence that this family of transposable elements has been significantly amplified
over the course of evolution. Angel elements and Xenopus MITEs carry common sequence motifs at their termini, indicating common origin and/or related mechanisms of transposition.
We present a model in which MITEs take advantage of the basic cellular mechanism of DNA replication for their amplification,
which is dependent on the characteristic inverted repeat structures of these elements. We propose that MITEs are genomic parasites
that transpose via a DNA intermediate, which forms by a folding-back of a single strand of DNA, that borrow all of the necessary
factors for their amplification from products encoded in the genomes in which they reside. DNA polymorphisms in different
lines of zebrafish were detected by PCR using Angel-specific primers, indicating that such elements, combined with other transposons in vertebrate genomes, will be useful molecular
tools for genome mapping and genetic analyses of mutations.
Received: 7 April 1998 / Accepted: 7 April 1998 相似文献
5.
Along the gene, nucleotides in various codon positions tend to exert a slight but observable influence on the nucleotide
choice at neighboring positions. Such context biases are different in different organisms and can be used as genomic signatures.
In this paper, we will focus specifically on the dinucleotide composed of a third codon position nucleotide and its succeeding
first position nucleotide. Using the 16 possible dinucleotide combinations, we calculate how well individual genes conform
to the observed mean dinucleotide frequencies of an entire genome, forming a distance measure for each gene. It is found that
genes from different genomes can be separated with a high degree of accuracy, according to these distance values.
In particular, we address the problem of recent horizontal gene transfer, and how imported genes may be evaluated by their
poor assimilation to the host's context biases. By concentrating on the third- and succeeding first position nucleotides,
we eliminate most spurious contributions from codon usage and amino-acid requirements, focusing mainly on mutational effects.
Since imported genes are expected to converge only gradually to genomic signatures, it is possible to question whether a gene
present in only one of two closely related organisms has been imported into one organism or deleted in the other. Striking
correlations between the proposed distance measure and poor homology are observed when Escherichia coli genes are compared to Salmonella typhi, indicating that sets of outlier genes in E. coli may contain a high number of genes that have been imported into E. coli, and not deleted in S. typhi.
Received: 16 January 2001 / Accepted: 30 August 2001 相似文献
6.
We compared deleted copies of the seven mauritiana subfamilies of mariner transposable elements in species of the Drosophilidae. All elements were detected by PCR using the inverted terminal repeats
of the Mos1 element of Drosophila mauritiana as primers. A higher frequency of breakpoints in the 5′ part of the element compared to the 3′ part was observed. Of the
27 deletions, 9 (33%) occurred between short direct repeats (SDR) of 5 to 8 bp. The SDRs can be at or close to the breakpoints
of the deletion. A deleted copy of D. simulans (St. Martin population) had three repeats of a motif present only once in the complete consensus sequence. The high frequency
of SDRs at or near the breakpoints of the deletions strongly suggests that some of them do not occur at random. Mechanisms
that might explain these deletions, such as unequal crossing-over, ectopic recombination, and abortive gap repair, are discussed.
Received: 22 December 2000 / Accepted: 12 July 2001 相似文献
7.
The 5.8 S subunit and flanking internal transcribed spacer (ITS) regions in nuclear ribosomal DNA (rDNA) from spores of Glomus mosseae FL156 and UK118 were amplified by polymerase chain reaction (PCR) using ITS1 and ITS4 as primers. The amplification product
from template DNA of UK118 was cloned and sequenced (569 bp); the amplified DNA from FL156 was sequenced directly (582 bp).
There was a 95% sequence similarity between DNAs amplified from the two isolates; in contrast, major dissimilarities with
partial sequences of seven other glomalean taxa were observed. Four oligonucleotide sequences unique to Glomus mosseae were identified as potential primers. Their specificity to Glomus mosseae was assessed by PCR amplification of genomic DNA from spores from 36 glomalean fungi: 13 isolates of Glomus mosseae, two Glomus monosporum, 10 other Glomus isolates, and 11 other glomalean taxa from each of four other genera. The Glomus mosseae isolates were from a broad range of temperate zone agricultural soils. Oligonucleotide pair GMOS1 : GMOS2 primed specific
amplification of an oligonucleotide sequence (approximately 400 bp) present in all Glomus mosseae isolates and two isolates of the closely related Glomus monosporum. This primer pair did not prime PCR when the template consisted of DNA from any of the other glomalean fungi or any of the
nonmycorrhizal controls. In addition, a 24-mer oligonucleotide, designated GMOS5, hybridized with Glomus mosseae and Glomus monosporum DNA amplified by PCR using primer pairs ITS1 : ITS4 and GMOS1 : GMOS2. Colony-blot assays showed that GMOS5 hybridized to
100% and 97% of E. coli pUC19 clones of amplification products from Glomus mosseae FL156 and UK118 DNA templates, respectively, indicating that nearly all clones contained an homologous sequence. GMOS5 was
used successfully to detect specifically Glomus mosseae in DNA extracted from colonized sudan grass (Sorghum sudanense L.) roots and amplified by PCR using the primer pair GMOS1 : GMOS2. The results confirm several previous indications that
Glomus mosseae and Glomus monosporum are indistinguishable taxonomic entities.
Accepted: 14 February 1998 相似文献
8.
Sawada H Kanaya S Tsuda M Suzuki F Azegami K Saitou N 《Journal of molecular evolution》2002,54(4):437-457
Phytopathogenic Pseudomonas syringae is subdivided into about 50 pathovars due to their conspicuous differentiation with regard to pathogenicity. Based on the
results of a phylogenetic analysis of four genes (gyrB, rpoD, hrpL, and hrpS), Sawada et al. (1999) showed that the ancestor of P. syringae had diverged into at least three monophyletic groups during its evolution. Physical maps of the genomes of representative
strains of these three groups were constructed, which revealed that each strain had five rrn operons which existed on one circular genome. The fact that the structure and size of genomes vary greatly depending on the
pathovar shows that P. syringae genomes are quite rich in plasticity and that they have undergone large-scale genomic rearrangements. Analyses of the codon
usage and the GC content at the codon third position, in conjunction with phylogenomic analyses, showed that the gene cluster
involved in phaseolotoxin synthesis (argK–tox cluster) expanded its distribution by conducting horizontal transfer onto the genomes of two P. syringae pathovars (pv. actinidiae and pv. phaseolicola) from bacterial species distantly related to P. syringae and that its acquisition was quite recent (i.e., after the ancestor of P. syringae diverged into the respective pathovars). Furthermore, the results of a detailed analysis of argK [an anabolic ornithine carbamoyltransferase (anabolic OCTase) gene], which is present within the argK–tox cluster, revealed the plausible process of generation of an unusual composition of the OCTase genes on the genomes of these
two phaseolotoxin-producing pathovars: a catabolic OCTase gene (equivalent to the orthologue of arcB of P. aeruginosa) and an anabolic OCTase gene (argF), which must have been formed by gene duplication, have first been present on the genome of the ancestor of P. syringae; the catabolic OCTase gene has been deleted; the ancestor has diverged into the respective pathovars; the foreign-originated
argK–tox cluster has horizontally transferred onto the genomes of pv. actinidiae and pv. phaseolicola; and hence two copies of only the anabolic OCTase genes (argK and argF) came to exist on the genomes of these two pathovars. Thus, the horizontal gene transfer and the genomic rearrangement were
proven to have played an important role in the pathogenic differentiation and diversification of P. syringae.
Received: 22 May 2001 / Accepted: 26 September 2001 相似文献
9.
Genomic trees have been constructed based on the presence and absence of families of protein-encoding genes observed in 27
complete genomes, including genomes of 15 free-living organisms. This method does not rely on the identification of suspected
orthologs in each genome, nor the specific alignment used to compare gene sequences because the protein-encoding gene families
are formed by grouping any protein with a pairwise similarity score greater than a preset value. Because of this all inclusive
grouping, this method is resilient to some effects of lateral gene transfer because transfers of genes are masked when the
recipient genome already has a homolog (not necessarily an ortholog) of the incoming gene. Of 71 genes suspected to have been
laterally transferred to the genome of Aeropyrum pernix, only approximately 7 to 15 represent genes where a lateral gene transfer appears to have generated homoplasy in our character
dataset. The genomic tree of the 15 free-living taxa includes six different bacterial orders, six different archaeal orders,
and two different eukaryotic kingdoms. The results are remarkably similar to results obtained by analysis of rRNA. Inclusion
of the other 12 genomes resulted in a tree only broadly similar to that suggested by rRNA with at least some of the differences
due to artifacts caused by the small genome size of many of these species. Very small genomes, such as those of the two Mycoplasma genomes included, fall to the base of the Bacterial domain, a result expected due to the substantial gene loss inherent to
these lineages. Finally, artificial ``partial genomes' were generated by randomly selecting ORFs from the complete genomes
in order to test our ability to recover the tree generated by the whole genome sequences when only partial data are available.
The results indicated that partial genomic data, when sampled randomly, could robustly recover the tree generated by the whole
genome sequences.
Received: 30 May 2001 / Accepted: 10 October 2001 相似文献
10.
Y. Yasui S. Nasuda Y. Matsuoka T. Kawahara 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2001,102(4):463-470
A novel plant short interspersed nuclear element (SINE) was identified in the second intron of the acetyl CoA carboxylase
gene of Aegilops umbellulata which has been designated ”Au”, for the host species in which it was discovered. Au elements have a tRNA-related region,
direct flanking repeats, and a short stretch of T at the 3′ end, which are features common to Au and previously characterized
SINEs. Au elements are detected in the genomes of several monocots and dicots by DNA dot hybridization and are also found
in the tobacco genome by database searching. Au elements are present at an especially high copy number (approximately 104 copies per haploid genome) in wheat and Ae. umbellulata. This suggests a recent amplification of Au in the Triticum and Aegilops species. In situ hybridization revealed a dispersed distribution of Au elements on wheat chromosomes. Au elements were amplified
by PCR from monocot and dicot species and the phylogenetic relationships among Au elements were inferred. This phylogenetic
analysis suggests amplification of Au elements in a manner consistent with the retrotransposon model for SINE dispersion.
The high copy number of Au elements and their dispersed distribution in wheat are desirable characteristics for a molecular
marker system in this important species.
Received: 15 April 2000 / Accepted: 24 August 2000 相似文献
11.
Characterization of MHC class I and β2-microglobulin sequences in Atlantic cod reveals an unusually high number of expressed class I genes 总被引:1,自引:1,他引:0
Degenerate polymerase chain reaction (PCR) primers based on conserved residues from alignments of species with already characterized
major histocompatibility complex (MHC)-encoded sequences were used in the search for class I and β2-microglobulin (b
2
m) genes in Atlantic cod (Gadus morhua L.). After PCR amplification and subsequent sequencing a putative class I sequence was identified, from which a probe was
designed and used to screen a spleen cDNA library from one single individual. The full-length clone obtained was sequenced
and shown to be a classical Mhc class I-encoded sequence. It revealed the characteristic α1-, α2-, and α3-domains and transmembrane and cytoplasmic region,
with several conserved amino acids. A PCR amplification from the α2-domain to the CY-region was performed on the same library,
using a proof-reading enzyme. At least 11 unique additional sequences were isolated. Moreover, sequencing of the additional
cDNA clones resulted in a total of 17 different Mhc class I sequences in this individual. A Southern hybridization of DNA from four different individuals using an α3-specific
probe confirmed this large number of genes. Interestingly, based on differences mainly in their transmembrane region, the
sequences obtained could be divided into two distinct groups. Within the groups no support could be obtained for any further
subdivision. Southern experiments using an α1-specific probe gave almost the same restriction fragment length polymorphism
with a high number of hybridizing bands, suggesting a low divergence in this part of the gene. Sequencing of PCR clones obtained
with a proof-reading enzyme confirmed this at the nucleotide level. PCR amplification to isolate and characterize the b
2
m gene resulted in a sequence which was used to screen a thymus cDNA library. Two different alleles were obtained and these
showed the characteristic features of known teleostean β2m sequences. A Southern hybridization with genomic DNA from four different individuals suggested the presence of one b
2
m locus in Atlantic cod.
Received: 10 March 1999 / Revised: 1 June 1999 相似文献
12.
Bouzat JL McNeil LK Robertson HM Solter LF Nixon JE Beever JE Gaskins HR Olsen G Subramaniam S Sogin ML Lewin HA 《Journal of molecular evolution》2000,51(6):532-543
We employed a phylogenomic approach to study the evolution of α subunits of the proteasome gene family from early diverging
eukaryotes. BLAST similarity searches of the Giardia lamblia genome identified all seven α proteasome genes characteristic of eukaryotes from the crown group. In addition, a PCR strategy
for the amplification of multiple α subunit sequences generated single α proteasome products for representatives of the Kinetoplastida
(Leishmania major), the Parabasalia (Trichomonas vaginalis), and the Microsporidia (Vairimorpha sp., Nosema sp., Endoreticulata sp., and Spraguea lophii). The kinetoplastid Trypanosoma cruzi and the eukaryote crown group Acanthamoeba castellanii yielded two distinct α proteasome genes each. The presence of seven distinct α proteasome genes in G. lamblia, one of the earliest-diverging eukaryotes, indicates that the α proteasome gene family evolved rapidly from a minimum of one
gene in Archaea to seven or more in Eukarya. Results from the phylogenomic analysis are consistent with the idea that the
Diplomonida (as represented by G. lamblia), the Kinetoplastida, the Parabasalia, and the Microsporidia diverged after the duplication events that originated the α
proteasome gene family. A model for the early origin and evolution of the proteasome gene family is presented.
Received: 14 February 2000 / Accepted: 14 August 2000 相似文献
13.
We have used the polymerase chain reaction (PCR) method to monitor meiotic recombination in the basidiomycete Coprinus cinereus. We used DNA-mediated transformation to recover strains with modifications of the trp1 locus. The modifications were designed to introduce unique PCR priming sites separated by a homologous 2.4 kb region in which
crossing over could occur. We showed that exchange occurred in this region at the frequency expected for a typical region
of this genome (2.4 kb should correspond to a genetic length of 0.08 cM). We also detected products resulting from crossing
over in DNAs extracted from cells in meiotic prophase. The assay should be useful for monitoring exchange in mutants that
cannot complete meiosis.
Received: 5 September 1996 / Accepted: 1 December 1996 相似文献
14.
We compared the codon usage of sequences of transposable elements (TEs) with that of host genes from the species Drosophila melanogaster, Arabidopsis thaliana, Caenorhabditis elegans, Saccharomyces cerevisiae, and Homo sapiens. Factorial correspondence analysis showed that, regardless of the base composition of the genome, the TEs differed from the
genes of their host species by their AT-richness. In all species, the percentage of A + T on the third codon position of the
TEs was higher than that on the first codon position and lower than that in the noncoding DNA of the genomes. This indicates
that the codon choice is not simply the outcome of mutational bias but is also subject to selection constraints. A tendency
toward higher A + T on the third position than on the first position was also found in the host genes of A. thaliana, C. elegans, and S. cerevisiae but not in those of D. melanogaster and H. sapiens. This strongly suggests that the AT choice is a host-independent characteristic common to all TEs. The codon usage of TEs
generally appeared to be different from the mean of the host genes. In the AT-rich genomes of Arabidopsis thaliana, Caenorhabditis elegans, and Saccharomyces cerevisiae, the codon usage bias of TEs was similar to that of weakly expressed genes. In the GC-rich genome of D. melanogaster, however, the bias in codon usage of the TEs clearly differed from that of weakly expressed genes. These findings suggest
that selection acts on TEs and that TEs may display specific behavior within the host genomes.
Received: 2 May 2001 / Accepted: 29 October 2001 相似文献
15.
Transferability of wheat microsatellites to diploid Triticeae species carrying the A, B and D genomes 总被引:8,自引:0,他引:8
P. Sourdille M. Tavaud G. Charmet M. Bernard 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2001,103(2-3):346-352
Hexaploid wheat (Triticum aestivum L em Thell) is derived from a complex hybridization procedure involving three diploid species carrying the A, B and D genomes.
In this study, we evaluated the ability of microsatellite sequences from T. aestivum to be revealed on different ancestral diploid species more or less closely related, i.e. to test for their transferability.
Fifty five primer pairs, evenly distributed all over the genome, were investigated. Forty three of them mapped to single loci
on the hexaploid wheat genetic map although only 20 (46%) gave single PCR products; the 23 others (54%) gave more than one
band with either only one being polymorphic, the others remaining monomorphic, or with several co-segregating polymorphic
bands. The other 12 detected two (9) or three (3) different loci. From the 20 primer pairs which gave one amplification pro-
duct on hexaploid wheat, nine (45%) also amplified products on only one of the diploid species, and seven (35%) on more than
one. Four microsatellites (20%) which mapped to chromosomes from the B genome of wheat, did not give any amplification signal
on any of the diploid species. This suggests that some regions of the B genome have evolved more rapidly compared to the A
or D genomes since the emergence of polyploidy, or else that the donor(s) of this B genome has(have) not yet been identified.
Our results confirm that Triticum monococcum ssp. urartu and Triticum tauschii were the main donors of the A and D genomes respectively, and that Aegilops speltoides is related to the ancestor(s) of the wheat polyploid B genome.
Received: 21 June 2000 / Accepted: 15 November 2000 相似文献
16.
Sakai H Imamura C Osada Y Saito R Washio T Tomita M 《Journal of molecular evolution》2001,52(2):164-170
In this study, we analyzed the correlation between codon usage bias and Shine–Dalgarno (SD) sequence conservation, using
complete genome sequences of nine prokaryotes. For codon usage bias, we adopted the codon adaptation index (CAI), which is
based on the codon usage preference of genes encoding ribosomal proteins, elongation factors, heat shock proteins, outer membrane
proteins, and RNA polymerase subunit proteins. To compute SD sequence conservation, we used SD motif sequences predicted by
Tompa and systematically aligned them with 5′UTR sequences. We found that there exists a clear correlation between the CAI
values and SD sequence conservation in the genomes of Escherichia coli, Bacillus subtilis, Haemophilus influenzae, Archaeoglobus fulgidus, Methanobacterium thermoautotrophicum, and Methanococcus jannaschii, and no relationship is found in M. genitalium, M. pneumoniae, and Synechocystis. That is, genes with higher CAI values tend to have more conserved SD sequences than do genes with lower CAI values in these
organisms. Some organisms, such as M. thermoautotrophicum, do not clearly show the correlation. The biological significance of these results is discussed in the context of the translation
initiation process and translation efficiency.
Received: 22 June 2000 / Accepted: 18 October 2000 相似文献
17.
A Simple Method for Developing Microsatellite Markers using Amplified Fragments of Inter-simple Sequence Repeat (ISSR) 总被引:21,自引:0,他引:21
10 A primer IP1 designed from the sequenced region at one end of the microsatellite and for nested PCR another primer IP2 based
on the sequence between IP1 and the microsatellite were prepared. These two primers were used to determine the other sequence
flanking the microsatellite by a “walking” method. With this approach, we developed several microsatellite markers from Salix reinii, Pinus densiflora and Robinia pseudoacacia, respectively. The absence of enrichment processes and screening procedures makes it easier to develop microsatellite markers,
and this approach provides an alternative for the development of microsatellite markers in any organism.
Received 23 April 2001/ Accepted in revised form 11 June 2001 相似文献
18.
Isaäc J. Nijman Patrick van Tessel Johannes A. Lenstra 《Journal of molecular evolution》2002,54(1):9-16
SINE retrotransposition events have proven their value as phylogenetic markers in several eukaryotic taxa at different taxonomic
levels. The genomes of ruminants contain three related SINE elements, Bov-tA, Bov-A2, and Bov-B. To estimate the time points
of retrotransposition of individual copies of these SINEs, we designed PCR primers on database sequences containing SINE insertions
in cattle, sheep, or goat genomes and tested for the presence of these copies in the genomes of other ruminants. It was checked
by sequencing whether length variation of the PCR products reflected a SINE retrotransposition. One Bov-B and nine Bov-tA
insertions were shared by cattle, sheep, goat, and giraffe, indicating an early retrotransposition event before the radiation
of the Pecora, while three other Bov-tA and two Bov-B elements were apparently inserted later. The ruminant α-lactalbumine
gene contains a hotspot of early and more recent Bov-tA insertions, a Bov-tA replacement as well as a recent Bov-B insertion.
Three Bov-A2 insertions were found to be shared only by the Bovidae, the Bovini, and the Bos and Bison species, respectively, indicating that most Bov-A2 insertions are relatively recent. The time elapsed since the retrotransposition
was also reflected in the degeneration of the direct repeats that flank SINE inserts. We suggest that retrotransposition of
SINEs may serve as phylogenetic markers in the ruminant families, subfamilies, and even tribes. In addition, sequencing of
SINE insertions revealed several other unique deletions/insertions that also may be informative for phylogenetic reconstructions
of ruminants.
Received: 19 January 2001 / Accepted: 6 June 2001 相似文献
19.
Identification of a chromosome-specific probe that maps within the Ph1 deletions in common and durum wheat 总被引:1,自引:0,他引:1
G. Segal B. Liu J. M. Vega S. Abbo M. Rodova M. Feldman 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,94(8):968-970
The Ph1 (pairing homoeologous) gene is the major factor that determines the diploid-like chromosome behavior of polyploid wheat.
This gene, which is located on the long arm of chromosome 5B (5BL), suppresses homoeologous pairing at meiosis while allowing
exclusive homologous pairing. In an effort to tag the specific chromosomal region where this gene is located, we have previously
microdissected chromosome arm 5BL from bread wheat and produced a plasmid library by random PCR amplification and cloning.
In this work we isolated from this library a 5BL-specific probe, WPG90, and mapped it within the interstitial deleted chromosome
fragments carrying Ph1 in common and durum wheat. A PCR assay of Ph1 based on WPG90 was developed that allows an easy identification of homozygous genotypes deficient for this gene.
Received: 19 June 1996 / Accepted: 18 October 1996 相似文献
20.
Whereas the genomes of many organisms contain several nonallelic types of linker histone genes, one single histone H1 type
is known in Drosophila melanogaster that occurs in about 100 copies per genome. Amplification of H1 gene sequences from genomic DNA of wild type strains of D. melanogaster from Oregon, Australia, and central Africa yielded numerous clones that all exhibited restriction patterns identical to each
other and to those of the known H1 gene sequence. Nucleotide sequences encoding the evolutionarily variable domains of H1
were determined in two gene copies of strain Niamey from central Africa and were found to be identical to the known H1 sequence.
Most likely therefore, the translated sequences of D. melanogaster H1 genes do not exhibit intragenomic or intergenomic variations.
In contrast, three different histone H1 genes were isolated from D. virilis and found to encode proteins that differ remarkably from each other and from the H1 of D. melanogaster and D. hydei. About 40 copies of H1 genes are organized in the D. virilis genome with copies of core histone genes in gene quintets that were found to be located in band 25F of chromosome 2. Another
type of histone gene cluster is present in about 15 copies per genome and contains a variable intergenic sequence instead
of an H1 gene. The H1 heterogeneity in D. virilis may have arisen from higher recombination rates than occur near the H1 locus in D. melanogaster and might provide a basis for formation of different chromatin subtypes.
Received: 2 March 2000 / Accepted: 1 June 2000 相似文献