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131.
132.
Gardner MJ Shallom SJ Carlton JM Salzberg SL Nene V Shoaibi A Ciecko A Lynn J Rizzo M Weaver B Jarrahi B Brenner M Parvizi B Tallon L Moazzez A Granger D Fujii C Hansen C Pederson J Feldblyum T Peterson J Suh B Angiuoli S Pertea M Allen J Selengut J White O Cummings LM Smith HO Adams MD Venter JC Carucci DJ Hoffman SL Fraser CM 《Nature》2002,419(6906):531-534
The mosquito-borne malaria parasite Plasmodium falciparum kills an estimated 0.7-2.7 million people every year, primarily children in sub-Saharan Africa. Without effective interventions, a variety of factors-including the spread of parasites resistant to antimalarial drugs and the increasing insecticide resistance of mosquitoes-may cause the number of malaria cases to double over the next two decades. To stimulate basic research and facilitate the development of new drugs and vaccines, the genome of Plasmodium falciparum clone 3D7 has been sequenced using a chromosome-by-chromosome shotgun strategy. We report here the nucleotide sequences of chromosomes 10, 11 and 14, and a re-analysis of the chromosome 2 sequence. These chromosomes represent about 35% of the 23-megabase P. falciparum genome. 相似文献
133.
134.
Mutations in genes encoding melanosomal proteins cause pigmentary glaucoma in DBA/2J mice. 总被引:11,自引:0,他引:11
Michael G Anderson Richard S Smith Norman L Hawes Adriana Zabaleta Bo Chang Janey L Wiggs Simon W M John 《Nature genetics》2002,30(1):81-85
Pigmentary glaucoma is a significant cause of human blindness. Abnormally liberated iris pigment and cell debris enter the ocular drainage structures, leading to increased intraocular pressure (IOP) and glaucoma. DBA/2J (D2) mice develop a form of pigmentary glaucoma involving iris pigment dispersion (IPD) and iris stromal atrophy (ISA). Using high-resolution mapping techniques, sequencing and functional genetic tests, we show that IPD and ISA result from mutations in related genes encoding melanosomal proteins. IPD is caused by a premature stop codon mutation in the Gpnmb (GpnmbR150X) gene, as proved by the occurrence of IPD only in D2 mice that are homozygous with respect to GpnmbR150X; otherwise, similar D2 mice that are not homozygous for GpnmbR150X do not develop IPD. ISA is caused by the recessive Tyrp1b mutant allele and rescued by the transgenic introduction of wildtype Tyrp1. We hypothesize that IPD and ISA alter melanosomes, allowing toxic intermediates of pigment production to leak from melanosomes, causing iris disease and subsequent pigmentary glaucoma. This is supported by the rescue of IPD and ISA in D2 eyes with substantially decreased pigment production. These data indicate that pigment production and mutant melanosomal protein genes may contribute to human pigmentary glaucoma. The fact that hypopigmentation profoundly alleviates the D2 disease indicates that therapeutic strategies designed to decrease pigment production may be beneficial in human pigmentary glaucoma. 相似文献
135.
Microsatellites are preferentially associated with nonrepetitive DNA in plant genomes. 总被引:36,自引:0,他引:36
Microsatellites are a ubiquitous class of simple repetitive DNA sequence. An excess of such repetitive tracts has been described in all eukaryotes analyzed and is thought to result from the mutational effects of replication slippage. Large-scale genomic and EST sequencing provides the opportunity to evaluate the abundance and relative distribution of microsatellites between transcribed and nontranscribed regions and the relationship of these features to haploid genome size. Although this has been studied in microbial and animal genomes, information in plants is limited. We assessed microsatellite frequency in plant species with a 50-fold range in genome size that is mostly attributable to the recent amplification of repetitive DNA. Among species, the overall frequency of microsatellites was inversely related to genome size and to the proportion of repetitive DNA but remained constant in the transcribed portion of the genome. This indicates that most microsatellites reside in regions pre-dating the recent genome expansion in many plants. The microsatellite frequency was higher in transcribed regions, especially in the untranslated portions, than in genomic DNA. Contrary to previous reports suggesting a preferential mechanism for the origin of microsatellites from repetitive DNA in both animals and plants, our findings show a significant association with the low-copy fraction of plant genomes. 相似文献
136.
王虹 《西安联合大学学报》2002,5(1):107-108
不同的物种是怎样进化形成不同的形态 ,这仍是现代进化生物学中研究的主要课题。近年来 ,对这一问题的研究已集中在由于进化时间的不同而导致进化机制变化的模型上 ,并在解开机体发育期间控制形态表现的分子机理方面取得了惊人的进展。值得注意的是 :形态的表型和一些调节基因的突变大致反映了物种间所表现的差异。通过分析生物的系统发育 ,重新构建系统发育史 ,可以阐明控制发育过程和进化发育的相关时间的遗传网络的分子进化机制。与系统发育进化有关的信息影印在组成它们的基因片段上。存在于这些发育位点的信息可以使人们追踪到发育调节… 相似文献
137.
近几年来,人类在所有科学领域取得成果的速率在惊人地加快。当我们拓展对地球的控制时,同时也在准备重塑和改造地球上的景观,为自己到地球外居住作准备。几个世纪以来,我们已经花大力改造了地球,现在,我们正准备把宇宙转变成一个充满生命的有生气的实体。我们将通过把我们的意识、技能、智力以及我们自身扩展到其他行星上来实现这个目标。我们把人类改变和改善地球环境(最终是宇宙本身)的努力总称为“生命化”。生命化是调节人类行为的一种力量,赋予地球并最终赋予整个宇宙以意识和智慧,是全部人类生产活动背后的原动力。然而,为… 相似文献
138.
The“cut-and-sewn” pressure garments are normally tailored made in various sizes according to the size of human body as well as the area of burn wounds.When a tubular pressure garment is cut in different length and width measurements,different aspect ratio will be occurred on the elastic fabric for making up the pressuregarment. Many therapists in Hong Kong concerned the change of aspect ratio may affect the tensile properties of the elastic fabric and ultimately will affect the skin-and-garment interface pressure for the patient.The aim of 相似文献
139.
Michael Steel 《Journal of Classification》1992,9(1):91-116
In taxonomy and other branches of classification it is useful to know when tree-like classifications on overlapping sets of
labels can be consistently combined into a parent tree. This paper considers the computation complexity of this problem. Recognizing
when a consistent parent tree exists is shown to be intractable (NP-complete) for sets of unrooted trees, even when each tree
in the set classifies just four labels. Consequently determining the compatibility of qualitative characters and partial binary
characters is, in general, also NP-complete. However for sets of rooted trees an algorithm is described which constructs the
“strict consensus tree” of all consistent parent trees (when they exist) in polynomial time. The related question of recognizing
when a set of subtrees uniquely defines a parent tree is also considered, and a simple necessary and sufficient condition
is described for rooted trees.
This work was supproted by the Alexander von Humoldt-Stiftung. I wish to thank Andreas Dress, Hans-Jürgen Bandelt and the
referees for their helpful comments. 相似文献
140.
Spectral analysis of phylogenetic data 总被引:12,自引:0,他引:12
The spectral analysis of sequence and distance data is a new approach to phylogenetic analysis. For two-state character sequences,
the character values at a given site split the set of taxa into two subsets, a bipartition of the taxa set. The vector which
counts the relative numbers of each of these bipartitions over all sites is called a sequence spectrum. Applying a transformation
called a Hadamard conjugation, the sequence spectrum is transformed to the conjugate spectrum. This conjugation corrects for
unobserved changes in the data, independently from the choice of phylogenetic tree. For any given phylogenetic tree with edge
weights (probabilities of state change), we define a corresponding tree spectrum. The selection of a weighted phylogenetic
tree from the given sequence data is made by matching the conjugate spectrum with a tree spectrum. We develop an optimality
selection procedure using a least squares best fit, to find the phylogenetic tree whose tree spectrum most closely matches
the conjugate spectrum. An inferred sequence spectrum can be derived from the selected tree spectrum using the inverse Hadamard
conjugation to allow a comparison with the original sequence spectrum.
A possible adaptation for the analysis of four-state character sequences with unequal frequencies is considered. A corresponding
spectral analysis for distance data is also introduced. These analyses are illustrated with biological examples for both distance
and sequence data. Spectral analysis using the Fast Hadamard transform allows optimal trees to be found for at least 20 taxa
and perhaps for up to 30 taxa.
The development presented here is self contained, although some mathematical proofs available elsewhere have been omitted.
The analysis of sequence data is based on methods reported earlier, but the terminology and the application to distance data
are new. 相似文献