共查询到20条相似文献,搜索用时 15 毫秒
1.
The intriguing diversity of highly abundant satellite repeats found even among closely related species can result from processes
leading to dramatic changes in copy number of a particular sequence in the genome and not from rapid accumulation of mutations.
To test this hypothesis, we investigated the distribution of the PRAT satellite DNA family, a highly abundant major satellite
in the coleopteran species Palorus ratzeburgii, in eight species belonging to the related genera (Tribolium, Tenebrio, Latheticus), the subfamily (Pimeliinae), and the family (Chrysomelidae). Dot blot analysis and PCR assay followed by Southern hybridization
revealed that the PRAT satellite, in the form of low-copy number repeats, was present in all tested species. The PRAT satellite
detected in the species Pimelia elevata has been sequenced, and compared with previously cloned PRAT monomers from Palorus ratzeburgii and Palorus subdepressus. Although the two Palorus species diverged at least 7 Myr ago, and the subfamily Pimeliinae separated from the genus Palorus 50–60 Myr ago, all PRAT clones exhibit high mutual homology, with average variability relative to the common consensus sequence
of 1.3%. The presence of ancestral mutations found in PRAT clones from all three species as well as the absence of species
diagnostic mutations illustrate extremely slow sequence evolution. This unexpectedly high conservation of PRAT satellite DNA
sequence might be induced by a small bias of turnover mechanisms favoring the ancestral sequence in the process of molecular
drive. 相似文献
2.
A PstI DNA family was isolated from the genome of a lacertid, Lacerta graeca. The 185-bp monomeric unit (pGPS) was cloned and hybridized to DNAs and chromosomes of several lacertid species. The data
showed that pGPS hybridizes to the (1) centromeric or pericentromeric heterochromatin of almost all the chromosomes of L. graeca and (2) genomic DNA of species phylogenetically related and unrelated to L. graeca. The presence of pGPS even in species immunologically apart more than 30 million years suggests that this repeated family
might be either very ancient or have been conserved during evolution due to its functional role. The latter hypothesis might
be supported by the results of sequence analysis which showed some homology with both several alphoid sequences of primates
and the CDEIII centromeric sequence of yeast. Segments of the satellite sequence are similar to the mammalian CENP-B box.
These observations suggest that pGPS might have a role in determining the centromeric function in lacertid lizards.
Received: 6 February 1997 / Accepted: 14 May 1997 相似文献
3.
The subspecies Chironomus thummi thummi and C. t. piger display dramatic differences in the copy number and chromosomal localization of a tandemly repeated DNA family (Cla elements).
In order to analyze the evolutionary dynamics of this repeat family, we studied the organization of Cla elements in the related
outgroup species C. luridus. We find three different patterns of Cla element organization in C. luridus, showing that Cla elements may be either strictly tandem-repetitive or be an integral part of two higher-order tandem repeats
(i.e., Hinf[lur] elements, Sal[lur] elements). All three types of Cla-related repeats are localized in the centromeres of C. luridus chromosomes. This suggests that the dispersed chromosomal localization of Cla elements in C. t. thummi may be the result of an amplification and transposition during evolution of this subspecies.
Received: 22 May 1996 / Accepted: 8 October 1996 相似文献
4.
Charles Lee Dean R. Court Charles Cho Jennifer L. Haslett Chyi-Chyang Lin 《Journal of molecular evolution》1997,44(3):327-335
Based on sequence analyses of 17 complete centromeric DNA monomers from ten different deer species, a model is proposed for
the genesis, evolution, and genomic organization of cervid satellite I DNA. All cervid satellite I DNA arose from the initial
amplification of a 31-bp DNA sequence. These 31-bp subrepeats were organized in a hierarchical fashion as 0.8-kb monomers
in plesiometacarpalia deer and 1-kb monomers in telemetacarpalia deer. The higher-order repeat nature of cervid centromeric
satellite DNA monomers accounts for their high intragenomic and intraspecific sequence conservation. Such high intraspecific
sequence conservation validates the use of a single cervid satellite I DNA monomer from each deer species for interspecific
sequence comparisons to elucidate phylogenetic relationships. Also, a specific 0.18-kb tandem duplication was observed in
all 1-kb monomers, implying that 1-kb cervid satellite I DNA monomers arose from an unequal crossover event between two similar
0.8-kb ancestral DNA sequences.
Received: 28 May 1996 / Accepted: 24 October 1996 相似文献
5.
Tachida H 《Journal of molecular evolution》2000,50(1):69-81
A simple nearly neutral mutation model of protein evolution was studied using computer simulation assuming a constant population
size. In this model, a gene consists of a finite number of codons and there is no recombination within a gene. Each codon
has two replacement and one silent sites. The fitness of a gene was determined multiplicatively by amino acids specified by
codons (the independent multicodon model). Nucleotide diversity at replacement sites decreases as selection becomes stronger.
A reduction of nucleotide diversity at silent sites also occurs as selection intensifies but the magnitude of the reduction
is not a monotone function of the intensity of selection. The dispersion index is close to one. The average value of Tajima's
and Fu and Li's statistics are negative and their absolute values increases as selection intensifies. However, their powers
of detecting selection under the present model were not high unless the number of sites is large or mutation rate is high.
The MK test was shown to detect intermediate selection fairly well. For comparison, the house-of-cards model was also investigated
and its behavior was shown to be more sensitive to changes of population size than that of the independent multicodon model.
The relevance of the present model for explaining protein evolution was discussed comparing its prediction and recent DNA
data.
Received: 24 May 1999 / Accepted: 17 August 1999 相似文献
6.
The recent completion of the sequencing of the Saccharomyces cerevisiae genome provides a unique opportunity to analyze the evolutionary relationships existing among the entire complement of retrotransposons
residing within a single genome. In this article we report the results of such an analysis of two closely related families
of yeast long terminal repeat (LTR) retrotransposons, Ty1 and Ty2. In our study, we analyzed the molecular variation existing
among the 32 Ty1 and 13 Ty2 elements present within the S. cerevisiae genome recently sequenced within the context of the yeast genome project. Our results indicate that while the Ty1 family
is most likely ancestral to Ty2 elements, both families of elements are relatively recent components of the S. cerevisiae genome. Our results also indicate that both families of elements have been subject to purifying selection within their protein
coding regions. Finally, and perhaps most interestingly, our results indicate that a relatively recent recombination event
has occurred between Ty2 and a subclass of Ty1 elements involving the LTR regulatory region. We discuss the possible biological
significance of these findings and, in particular, how they contribute to a better overall understanding of LTR retrotransposon
evolution.
Received: 30 September 1997 / Accepted: 3 February 1998 相似文献
7.
Philippe Castagnone-Sereno Hélène Leroy Jean-Philippe Semblat Frédéric Leroy Pierre Abad Carolien Zijlstra 《Journal of molecular evolution》1998,46(2):225-233
An AluI satellite DNA family has been isolated in the genome of the root-knot nematode Meloidogyne chitwoodi. This repeated sequence was shown to be present at approximately 11,400 copies per haploid genome, and represents about 3.5%
of the total genomic DNA. Nineteen monomers were cloned and sequenced. Their length ranged from 142 to 180 bp, and their A
+ T content was high (from 65.7 to 79.1%), with frequent runs of As and Ts. An unexpected heterogeneity in primary structure
was observed between monomers, and multiple alignment analysis showed that the 19 repeats could be unambiguously clustered
in six subfamilies. A consensus sequence has been deduced for each subfamily, within which the number of positions conserved
is very high, ranging from 86.7% to 98.6%. Even though blocks of conserved regions could be observed, multiple alignment of
the six consensus sequences did not enable the establishment of a general unambiguous consensus sequence. Screening of the
six consensus sequences for evidence of internal repeated subunits revealed a 6-bp motif (AAATTT), present in both direct
and inverted orientation. This motif was found up to nine times in the consensus sequences, also with the occurrence of degenerated
subrepeats. Along with the meiotic parthenogenetic mode of reproduction of this nematode, such structural features may argue
for the evolution of this satellite DNA family either (1) from a common ancestral sequence by amplification followed by mechanisms
of sequence divergence, or (2) through independent mutations of the ancestral sequence in isolated amphimictic nematode populations
and subsequent hybridization events. Overall, our results suggest the ancient origin of this satellite DNA family, and may
reflect for M. chitwoodi a phylogenetic position close to the ancestral amphimictic forms of root-knot nematodes.
Received: 23 April 1997 / Accepted: 9 July 1997 相似文献
8.
Contribution of Mutation and RNA Recombination to the Evolution of a Plant Pathogenic RNA 总被引:10,自引:0,他引:10
Miguel A. Aranda Aurora Fraile Joaquín Dopazo José M. Malpica Fernando García-Arenal 《Journal of molecular evolution》1997,44(1):81-88
The nucleotide sequence of 17 variants of the satellite RNA of cucumber mosaic virus (CMV-satRNA) isolated from field-infected
tomato plants in the springs of 1989, 1990, and 1991 was determined. The sequence of each of the 17 satRNAs was unique and
was between 334 and 340 nucleotides in length; 57 positions were polymorphic. There was much genetic divergence, ranging from
0.006 to 0.141 nucleotide substitutions per site for pairwise comparisons, and averaging 0.074 for any pair. When the polymorphic
positions were analyzed relative to a secondary structure model proposed for CMV-satRNAs, it was found that there were significantly
different numbers of changes in base-paired and non–base-paired positions, and that mutations that did not disrupt base pairing
were preferred at the putatively paired sites. This supports the concept that the need to maintain a functional structure
may limit genetic divergence of CMV-satRNA. Phylogenetic analyses showed that the 17 CMV-satRNA variants clustered into two
subgroups, I and II, and evolutionary lines proceeding by the sequential accumulation of mutations were apparent. Three satRNA
variants were outliers for these two phylogenetic groups. They were shown to be recombinants of subgroup I and II satRNAs
by calculating phylogenies for different molecular regions and by using Sawyer's test for gene conversion. At least two recombination
events were required to produce these three recombinant satRNAs. Thus, recombinants were found to be frequent (∼17%) in natural
populations of CMV-satRNA, and recombination may make an important contribution to the generation of new variants. To our
knowledge this is the first report of data allowing the frequency of recombinant isolates in natural populations of an RNA
replicon to be estimated.
Received: 14 May 1996 / Accepted: 17 July 1996 相似文献
9.
In eight hagfish species, it is known that chromosome elimination occurs during early embryogenesis, and some highly repetitive
DNA families, restricted to germ cells, have been isolated. One of these families, ``EEEo2,' has been isolated as DNA fragments
by restriction enzyme analyses from Eptatretus okinoseanus and E. cirrhatus. In this study, EEEo2 sequences were isolated from germline DNA in E. burgeri, Paramyxine sheni, and P. atami using PCR methods. Sequence analysis revealed that these sequences are intraspecifically homogeneous, except in E. burgeri, and are interspecifically conserved with heterogeneity. The intraspecific sequence variability tends to decrease as the copy
number increases. These results indicate that EEEo2 has evolved in a concerted manner. Moreover, an ancestral repeating motif
consisting of triplicate subrepeats was deduced. These results suggest that EEEo2 arose as an initial amplification of this
subrepeat and has evolved by saltatory replication. Phylogenetic analyses suggested the possibility that EEEo2 in E. okinoseanus and E. cirrhatus has been subjected to strong homogenizing forces for concerted evolution, whereas the force is weak in E. burgeri. In addition, EEEo2 in P. sheni and P. atami appear to have been incompletely subjected to these forces. Chromosomal in situ hybridization experiments revealed that EEEo2
sequences were located along almost their entire length of several heterochromatic chromosomes that are restricted to germ
cells. These chromosomes are disposed to form a secondary association during the first meiotic metaphases, except in P. sheni. This chromosomal distribution may promote a concerted mode of sequence evolution in both nonhomologous chromosomes and homologous
chromosomes and reflect the differential driving forces between species.
Received: 17 April 1999 / Accepted: 10 September 1999 相似文献
10.
Albert Jeltsch 《Journal of molecular evolution》1999,49(1):161-164
Circular permutations of genes during molecular evolution often are regarded as elusive, although a simple model can explain
these rearrangements. The model assumes that first a gene duplication of the precursor gene occurs in such a way that both
genes become fused in frame, leading to a tandem protein. After generation of a new start codon within the 5′ part of the
tandem gene and a stop at an equivalent position in the 3′ part of the gene, a protein is encoded that represents a perfect
circular permutation of the precursor gene product. The model is illustrated here by the molecular evolution of adenine-N6 DNA methyltransferases. β- and γ-type enzymes of this family can be interconverted by a single circular permutation event.
Interestingly, tandem proteins, proposed as evolutionary intermediates during circular permutation, can be directly observed
in the case of adenine methyltransferases, because some enzymes belonging to type IIS, like the FokI methyltransferase, are built up by two fused enzymes, both of which are active independently of each other. The mechanism
for circular permutation illustrated here is very easy and applicable to every protein. Thus, circular permutation can be
regarded as a normal process in molecular evolution and a changed order of conserved amino acid motifs should not be interpreted
to argue against divergent evolution.
Received: 17 November 1998 / Accepted: 19 February 1999 相似文献
11.
The extracellular hemoglobins of cladocerans derive from the aggregation of 12 two-domain globin subunits that are apparently
encoded by four genes. This study establishes that at least some of these genes occur as a tandem array in both Daphnia magna and Daphnia exilis. The genes share a uniform structure; a bridge intron separates two globin domains which each include three exons and two
introns. Introns are small, averaging just 77 bp, but a longer sequence (2.2–3.2 kb) separates adjacent globin genes. A survey
of structural diversity in globin genes from other daphniids revealed three independent cases of intron loss, but exon lengths
were identical, excepting a 3-bp insertion in exon 5 of Simocephalus. Heterogeneity in the extent of nucleotide divergence was marked among exons, largely as a result of the pronounced diversification
of the terminal exon. This variation reflected, in part, varying exposure to concerted evolution. Conversion events were frequent
in exons 1–4 but were absent from exons 5 and 6. Because of this difference, the results of phylogenetic analyses were strongly
affected by the sequences employed in this construction. Phylogenies based on total nucleotide divergence in exons 1–4 revealed
affinities among all genes isolated from a single species, reflecting the impact of gene conversion events. In contrast, phylogenies
based on total nucleotide divergence in exons 5 and 6 revealed affinities among orthologous genes from different taxa.
Received: 8 March 1999 / Accepted: 14 July 1999 相似文献
12.
We have examined the length distribution of perfect dimer repeats, where perfect means uninterrupted by any other base, using
data from GenBank on primates and rodents. Virtually no lengths greater than 30 repeats are found, except for rodent AG repeats,
which extend to 35. Comparable numbers of long AC and AG repeats suggest that they have not been selected for special functions
or DNA structures. We have compared the data with predictions of two models: (1) a Bernoulli Model in which bases are assumed
equally likely and distributed at random and (2) an Unbiased Random Walk Model (URWM) in which repeats are permitted to change
length by plus or minus one unit, with equal probabilities, and in which base substitutions are allowed to destroy long perfect
repeats, producing two shorter perfect repeats. The source of repeats is assumed to be from single base substutions from neighboring
sequences, i.e., those differing from the perfect repeat by a single base. Mutation rates either independent of repeat length
or proportional to length were considered. An upper limit to the lengths L≈ 30 is assumed and isolated dimers are assumed unable to expand, so that there are absorbing barriers to the random walk
at lengths 1 and L+ 1, and a steady state of lengths is reached. With these assumptions and estimated values for the rates of length mutation
and base substitution, reasonable agreement is found with the data for lengths > 5 repeats. Shorter repeats, of lengths ≤
3 are in general agreement with the Bernoulli Model. By reducing the rate of length mutations for n≤ 5, it is possible to obtain reasonable agreement with the full range of data. For these reduced rates, the times between
length mutations become comparable to those suggested for a bottleneck in the evolution of Homo sapiens, which may be the reason for low heterozygosity of short repeats. 相似文献
13.
Jih-Shiou Liu Yau-Heiu Hsu Tzu-Yu Huang Na-Sheng Lin 《Journal of molecular evolution》1997,44(2):207-213
Satellite RNA of bamboo mosaic potexvirus (satBaMV) is a linear RNA molecule which encodes a 20-kDa nonstructural protein.
Sequences of seven different satBaMV isolates from bamboo hosts in three genera showed 0.7% to 7.5% base variation which spanned
the whole RNA molecule. However, the putative 20-kDa open reading frame was all preserved in these isolates. The phylogenetic
relationship based on the nucleotide sequence did not show particular grouping of satBaMV from the host in one genus; neither
was the grouping of satBaMV evident by location of sampling. Putative secondary structures of the 3′ untranslated regions
showed a basic pattern with conserved hexanucleotides (ACCUAA) and polyadenylation signal (AAUAAA) located in the loop regions.
Although the satBaMV-encoded 20-kDa protein is a nonstructural protein, its predicted secondary structure contains eight-stranded
β-sheets which may form ``jelly-roll' structure similar to that found in capsid protein encoded by satellite virus of panicum
mosaic virus.
Received: 26 June 1996 / Accepted: 9 September 1996 相似文献
14.
The polymeric ubiquitin (poly-u) genes are composed of tandem 228-bp repeats with no spacer sequences between individual
monomer units. Ubiquitin is one of the most conserved proteins known to date, and the individual units within a number of
poly-u genes are significantly more similar to each other than would be expected if each unit evolved independently. It has
been proposed that the rather striking similarity among poly-u monomers in some lineages is caused by a series of homogenization
events. Here we report the sequences of the polyubiquitin-C (Ubc) genes in two mouse strains. Analysis of these sequences,
as well as those of the previously reported Chinese hamster and rat poly-u genes, supports the assertion that the homogenization
of the ubiquitin-C gene in rodents is due to unequal crossing-over events. The sequence divergence of noncoding DNA was used
to estimate the frequency of unequal crossing-over events (6.3 × 10−5 events per generation) in the Ubc gene, as well as to provide evidence of apparent selection in the poly-u gene. 相似文献
15.
A mitochondrial DNA (mtDNA) phylogeny of cichlid fish is presented for the most taxonomically inclusive data set compiled
to date (64 taxa). 16S rDNA data establish with confidence relationships among major lineages of cichlids, with a general
pattern congruent with previous morphological studies and less inclusive molecular phylogenies based on nuclear genes. Cichlids
from Madagascar and India are the most basal groups of the family Cichlidae and sister to African–Neotropical cichlids. The
cichlid phylogeny suggests drift-vicariance events, consistent with the fragmentation of Gondwana, to explain current biogeographic
distributions. Important phylogenetic findings include the placement of the controversial genus Heterochromis basal among African cichlids, the South American genus Retroculus as the most basal taxon of the Neotropical cichlid assemblage, and the close relationship of the Neotropical genera Cichla with Astronotus rather than with the crenicichlines. Based on a large number of South American genera, the Neotropical cichlids are defined
as a monophyletic assemblage and shown to harbor significantly higher levels of genetic variation than their African counterparts.
Relative rate tests suggest that Neotropical cichlids have experienced accelerated rates of molecular evolution. But these
high evolutionary rates were significantly higher among geophagine cichlids.
Received: 18 September 1998 / Accepted: 16 December 1998 相似文献
16.
The 1.709 or satellite IV repeated DNA family originally isolated from the domestic cow was analyzed using Southern blotting, pulsed field gel electrophoresis, fluorescence in situ hybridization, and DNA sequencing in species belonging to the genera Bos, Bison, Bubalus, Syncerus, Boselaphus, and Tragelaphus. Hybridization indicates that the family has been amplified in Bos, Bison, Bubalus, and Syncerus but not in Boselaphus or Tragelaphus. Pericentromeric, higher-order repeat substructure exists in all species, with multimeric arrays ranging in size from 10 to 1500 kb. Sequence analysis of a 492-bp PCR product revealed comparable levels (0.2–4.5%) of intra- and interspecific divergence when species of Bos and Bison were compared, supporting the idea that species of these two genera should be recognized under the genus Bos. Alternatively, all Syncerus sequences cluster as a monophyletic group on an evolutionary tree and differ from those of Bos/Bison by about 13%. Comparing these findings with the fossil record indicates that concerted evolution has occurred since Bos/Bison and Syncerus last shared a common ancestor (5.0 MYA) but before the radiation of the genus Bos (2.5 MYA): GenBank accession numbers AY517856-AY517904.
Pfizer Global Research and Development, Department of Pathology, Eastern Point Road, Groton, CT 06340, USA 相似文献
17.
Allan M. Crawford Steven M. Kappes Korena A. Paterson Mauricio J. deGotari Ken G. Dodds Brad A. Freking Roger T. Stone Craig W. Beattie 《Journal of molecular evolution》1998,46(2):256-260
Previous studies suggest the median allele length of microsatellites is longest in the species from which the markers were
derived, suggesting that an ascertainment bias was operating. We have examined whether the size distribution of microsatellite
alleles between sheep and cattle is source dependent using a set of 472 microsatellites that can be amplified in both species.
For those markers that were polymorphic in both species we report a significantly greater number of markers (P < 0.001) with longer median allele sizes in sheep, regardless of microsatellite origin. This finding suggests that any ascertainment
bias operating during microsatellite selection is only a minor contributor to the variation observed.
Received: 6 January 1997 / Accepted: 19 May 1997 相似文献
18.
Liao D 《Journal of molecular evolution》2000,51(4):305-317
Multiple copies of a given ribosomal RNA gene family undergo concerted evolution such that sequences of all gene copies are
virtually identical within a species although they diverge normally between species. In eukaryotes, gene conversion and unequal
crossing over are the proposed mechanisms for concerted evolution of tandemly repeated sequences, whereas dispersed genes
are homogenized by gene conversion. However, the homogenization mechanisms for multiple-copy, normally dispersed, prokaryotic
rRNA genes are not well understood. Here we compared the sequences of multiple paralogous rRNA genes within a genome in 12
prokaryotic organisms that have multiple copies of the rRNA genes. Within a genome, putative sequence conversion tracts were
found throughout the entire length of each individual rRNA genes and their immediate flanks. Individual conversion events
convert only a short sequence tract, and the conversion partners can be any paralogous genes within the genome. Interestingly,
the genic sequences undergo much slower divergence than their flanking sequences. Moreover, genomic context and operon organization
do not affect rRNA gene homogenization. Thus, gene conversion underlies concerted evolution of bacterial rRNA genes, which
normally occurs within genic sequences, and homogenization of flanking regions may result from co-conversion with the genic
sequence.
Received: 31 March 2000 / Accepted: 15 June 2000 相似文献
19.
The polyubiquitin gene, encoding tandemly repeated multiple ubiquitins, constitutes a uniquitin gene subfamily. It has been
demonstrated that polyubiquitin genes are subject to concerted evolution; namely, the individual ubiquitin coding units contained
within a polyubiquitin gene are more similar to one another than they are to the ubiquitin coding units in the orthologous
gene from other species. However there has been no comprehensive study on the concerted evolution of polyubiquitin genes in
a wide range of species, because the relationships (orthologous or paralogous) among multiple polyubiquitin genes from different
species have not been extensively analyzed yet. In this report, we present the results of analyzing the nucleotide sequence
of polyubiquitin genes of mammals, available in the DDBJ/EMBL/GenBank nucleotide sequence databases, in which we found that
there are two groups of polyubiquitin genes in an orthologous relationship. Based on this result, we analyzed the concerted
evolution of the polyubiquitin gene in various species and compared the frequency of concerted evolutionary events interspecifically
by taking into consideration that the rate of synonymous substitution at the polyubiquitin gene locus may vary depending on
species. We found that the concerted evolutionary events in polyubiquitin genes have been more frequent in rats and Chinese
hamsters than those in humans, cows, and sheep. The guinea pig polyubiquitin gene was an intermediate example. The frequency
of concerted evolution in the mouse gene was unexpectedly low compared to that of other rodent genes.
Received: 18 January 2000 / Accepted: 26 April 2000 相似文献
20.
Sybille Kubis John Seymour Heslop-Harrison Thomas Schmidt 《Journal of molecular evolution》1997,44(3):310-320
Members of a highly abundant restriction satellite family have been isolated from the wild beet species Beta nana. The satellite DNA sequence is characterized by a conserved RsaI restriction site and is present in three of four sections of the genus Beta, namely Nanae, Corollinae, and Beta. It was not detected in species of the evolutionary old section Procumbentes, suggesting its amplification after separation of this section. Sequences of eight monomers were aligned revealing a size
variation from 209 to 233 bp and an AT content ranging from 56.5% to 60.5%. The similarity between monomers in B. nana varied from 77.7% to 92.2%. Diverged subfamilies were identified by sequence analysis and Southern hybridization. A comparative
study of this repetitive DNA element by fluorescent in situ hybridization and Southern analyses in three representative species
was performed showing a variable genomic organization and heterogeneous localizations along metaphase chromosomes both within
and between species. In B. nana the copy number of this satellite, with some 30,000 per haploid genome, is more than tenfold higher than in Beta lomatogona and up to 200 times higher than in Beta vulgaris, indicating different levels of sequence amplification during evolution in the genus Beta. In sugar beet (B. vulgaris), the large-scale organization of this tandem repeat was examined by pulsed-field gel electrophoresis. Southern hybridization
to genomic DNA digested with DraI demonstrated that satellite arrays are located in AT-rich regions and the tandem repeat is a useful probe for the detection
of genetic variation in closely related B. vulgaris cultivars, accessions, and subspecies.
Received: 24 May 1996 / Accepted: 13 September 1996 相似文献