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151.
A swimy locus derived from a novel DNA transposon Zisupton was located on the sex determination region (SD) of Xiphophorus maculatus. The analysis of expression pattern showed that swimy was exclusively expressed in adult testis in X. maculatus. The putative 939 aa sequence contains four Zn-finger domains, such as two C2H2 type, one NFX type and one SWIM type Zn-finger domain, and one SAP DNA-binding domain. Swimy has about 7 copies per haploid X. maculatus genome with Y-specific copies located in the SD region, and become the second new W-linked marker of platyfish. Analysis of the structure and distribution of this sex-linked marker is benefit to shed new light on the evolutionary dynamics of sex chromosomes in fish. 相似文献
152.
Prof. Gerhart U. Ryffel 《Biotechnology journal》2012,7(11):1328-1331
Based on recent advances in plant gene technology, I propose to develop a new category of GM plants, orgenic plants, that are compatible with organic farming. These orgenic plants do not contain herbicide resistance genes to avoid herbicide application in agriculture. Furthermore, they either contain genes that are naturally exchanged between species, or are sterile to avoid outcrossing if they received a transgene from a different species. These GM plants are likely to be acceptable to most sceptics of GM plants and facilitate the use of innovative new crops. 相似文献
153.
Humulus lupulus is commonly known as hops, a member of the family moraceae. Currently many projects are underway leading to the accumulation of voluminous genomic and expressed sequence tag sequences in public databases. The genetically characterized domains in these databases are limited due to non-availability of reliable molecular markers. The large data of EST sequences are available in hops. The simple sequence repeat markers extracted from EST data are used as molecular markers for genetic characterization, in the present study. 25,495 EST sequences were examined and assembled to get full-length sequences. Maximum frequency distribution was shown by mononucleotide SSR motifs i.e. 60.44% in contig and 62.16% in singleton where as minimum frequency are observed for hexanucleotide SSR in contig (0.09%) and pentanucleotide SSR in singletons (0.12%). Maximum trinucleotide motifs code for Glutamic acid (GAA) while AT/TA were the most frequent repeat of dinucleotide SSRs. Flanking primer pairs were designed in-silico for the SSR containing sequences. Functional categorization of SSRs containing sequences was done through gene ontology terms like biological process, cellular component and molecular function. 相似文献
154.
Models for meiotic recombination based on Crick's “unpairing postulate” require symmetrical extrusion of stem-loop structures from homologous DNA duplexes. The potential for such extrusion is abundant in many species and, for a given single-strand segment, can be quantitated as the “folding of natural sequence” (FONS) energy value. This, in turn, can be decomposed into base order-dependent and base composition-dependent components. The FONS values of top and bottom strands in most Caenorhabditis elegans segments are close, as are the corresponding base order-dependent and base composition-dependent components; any discrepancies are in the base composition-dependent component. This suggests that the strands would extrude with similar kinetics. However, interspersed among these segments and at the ends of chromosomes (telomeres) are segments containing short tandem repeats (microsatellites) which, by virtue of their high variability, have been postulated to inhibit the pairing of homologous chromosomes and hence drive speciation. In these segments, there are usually wide discrepancies between the FONS values of top and bottom strands, mainly attributable to differences in base order-dependent components. Analyses of artificial microsatellites of different unit sizes and base compositions show that this asymmetrical distribution of folding potential is greatest for microsatellites when the units are short and violate Chargaff's second parity rule. It is proposed that when there is folding asymmetry, recombination proceeds by special, strand-biased, somatic mechanisms analogous to those operating with Chi sequences in Escherichia coli. If meiotic recombination in the germ-line requires extrusion symmetry, then a general inhibitory influence of microsatellite-containing segments could mask the antirecombinational influence of their variability. Thus, microsatellites may not have driven speciation. 相似文献
155.
High levels of genetic diversity are generated in Haemophilus influenzae populations through DNA repeat-mediated phase variation and recombination with DNA fragments acquired by uptake from the external milieu. Conversely, multiple pathways for maintenance of the genome sequence are encoded in H. influenzae genomes. In Escherichia coli, mutations in single-stranded-DNA exonucleases destabilise tandem DNA repeats whilst inactivation of recG can stabilise repeat tracts. These enzymes also have varying effects on recombination. Deletion mutations were constructed in H. influenzae genes encoding homologs of ExoI, RecJ and RecG whilst ExoVII was refractory to mutation. Inactivation of RecJ and RecG, but not ExoI, increased sensitivity to irradiation with ultraviolet light. An increase in spontaneous mutation rate was not observed in single mutants but only when both RecJ and ExoI were mutated. None of the single- or double-mutations increased or decreased the rates of slippage in tetranucleotide repeat tracts. Furthermore, the exonuclease mutants did not exhibit significant defects in horizontal gene transfer. We conclude that RecJ, ExoI and RecG are required for maintenance of the H. influenzae genome but none of these enzymes influence the generation of genetic diversity through mutations in the tetranucleotide repeat tracts of this species. 相似文献
156.
Although microsatellite mutation rates generally increase with increasing length of the repeat tract, interruptions in a microsatellite may stabilize it. We have performed a direct analysis of the effect of microsatellite interruptions on mutation rate and spectrum in cultured mammalian cells. Two mononucleotide sequences (G17 and A17) and a dinucleotide [(CA)17] were compared with interrupted repeats of the same size and with sequences of 8 repeat units. MMR-deficient (MMR−) cells were used for these studies to eliminate effects of this repair process. Mutation rates were determined by fluctuation analysis on cells containing a microsatellite sequence at the 5′ end of an antibiotic-resistance gene; the vector carrying this sequence was integrated in the genome of the cells. In general, interrupted sequences had lower mutation rates than perfect ones of the same size, but the magnitude of the difference was dependent upon the sequence of the interrupting base(s). Some interrupted repeats had mutation rates that were lower than those of perfect sequences of the same length but similar to those of half the length. This suggests that interrupting bases effectively divide microsatellites into smaller repeat runs with mutational characteristics different from those of the corresponding full-length microsatellite. We conclude that interruptions decrease microsatellite mutation rate and influence the spectrum of frameshift mutations. The sequence of the interrupting base(s) determines the magnitude of the effect on mutation rate. 相似文献
157.
Catalina Monzón-Argüello Joaquín Muñoz Adolfo Marco Luis Felipe López-Jurado Ciro Rico 《Conservation Genetics》2008,9(4):1045-1049
We describe 12 new polymorphic dinucleotide microsatellite loci and multiplex Polymerase Chain Reaction conditions from the
loggerhead sea turtle Caretta caretta. Levels of polymorphism were assessed in 50 individuals from the nesting population of the Cape Verde Islands. Number of
alleles ranged from 3 to 13 (average of 7.33) and the values of observed heterozygosities from 0.32 to 0.80 (average of 0.61).
Cross-species amplification on three other marine turtles, Chelonia mydas, Eretmochelys imbricata and Dermochelys coriacea, revealed polymorphism and variability at eight, eleven and three loci, respectively. 相似文献
158.
X. Wang R. Trigiano M. Windham B. Scheffler T. Rinehart J. Spiers 《Tree Genetics & Genomes》2008,4(3):461-468
Abundant, codominant simple sequence repeats (SSRs) markers can be used for constructing genetic linkage maps and in marker-assisted
breeding programs. Enrichment methods for SSR motifs were optimized with the ultimate aim of developing numerous loci in flowering
dogwood (C. florida L.) genome. Small insert libraries using four motifs (GT, CT, TGG, and AAC) were constructed with C. florida ‘Cherokee Brave’ deoxyribonucleic acid (DNA). Colony polymerase chain reaction (PCR) of 2,208 selected clones with three
primers we reported previously indicated that 47% or 1,034 of the clones harbored one of the four targeted SSR motifs. Sequencing
the putative positive clones confirmed that nearly 99% (1,021 of 1,034) of them contained the desired motifs. Of the 871 unique
SSR loci, 617 were dinucleotide repeats (70.8%), and 254 were trinucleotide or longer repeats (29.2%). In total, 379 SSR loci
had perfect structure, 237 had interrupted, and 255 had compound structure. Primer pairs were designed from 351 unique sequences.
The ability of the 351 SSR primer pairs to amplify specific loci was evaluated with genomic DNA of ‘Appalachian Spring’ and
‘Cherokee Brave’. Of these primers, 311 successfully amplified product(s) with ‘Cherokee Brave’ DNA, 21 produced weak or faint
products, and 19 did not amplify any products. Additionally, 218 of the 311 primers pairs revealed polymorphisms between the
two cultivars, and 20 out of 218 primers detected an average of 13.7 alleles from 38 selected Cornus species and hybrids. These SSR loci constitute a valuable resource of ideal markers for both genetic linkage mapping and
gene tagging of flowering dogwood.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
159.
Muraguchi H Abe K Nakagawa M Nakamura K Yanagi SO 《Molecular genetics and genomics : MGG》2008,280(3):223-232
A Coprinopsis cinerea homokaryotic fruiting strain was mutagenised, identifying a mutant that exhibited a hyphal growth temperature sensitive defect and hyphal knot development defect at an early fruiting stage, even at the hyphal growth permissive temperature. Microscopic observation suggested that the mutant nuclei exhibited defects in the metaphase to anaphase transition at the restrictive temperature. The gene in which the mutation occurred was cloned, sequenced and determined to be homologous to smc1. Sequence analyses of the mutant revealed deletion of 28 base pairs in the 19th intron of the Cc.smc1 gene, resulting in complete failure of splicing of that intron and in insertion of 14 amino acids in the C-terminal region of the Cc.Smc1 protein. We isolated eight hyphal growth revertants and identified four intragenic suppressors. All were the result of amino acid substitutions in the C-terminal region. Three of the suppressors caused reversion of the arrest in an early fruiting stage. One of the suppressors exhibited cold sensitivity and failed to suppress the fruiting defect, suggesting that flexibility of a lobe in the C-terminal region is important for proper function of Cc.Smc1. 相似文献
160.
Short tandem repeats (STRs) are subjected to two kinds of mutational modifications: point mutations and replication slippages.
The latter is found to be the more frequent cause of STR modifications, but a satisfactory quantitative measure of the ratio
of the two processes has yet to be determined. The comparison of entire genome sequences of closely enough related species
enables one to obtain sufficient statistics by counting the differences in the STR regions. We analyzed human–chimpanzee DNA
sequence alignments to obtain the counts of point mutations and replication slippage modifications. The results were compared
with the results of a computer simulation, and the parameters quantifying the replication slippage probability as well as
the probabilities of point mutations within the repeats were determined. It was found that within the STRs with repeated units
consisting of one, two or three nucleotides, point mutations occur approximately twice as frequently as one would expect on
the basis of the 1.2% difference between the human and chimpanzee genomes. As expected, the replication slippage probability
is negligible below a 10-bp threshold and grows above this level. The replication slippage events outnumber the point mutations
by one or two orders of magnitude, but are still lower by one order of magnitude relative to the mutability of the markers
that are used for genotyping purposes. 相似文献