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Topic: Positive selection

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In the News (Tue 23 Apr 19)

 Evolution - Wikipedia, the free encyclopedia
The relative importance of natural selection and genetic drift in determining the fate of new mutations also depends on the population size and the strength of selection: when N times s (population size times strength of selection) is small, genetic drift predominates.
Sexual selection occurs when organisms which are more attractive to the opposite sex because of their features reproduce more and thus increase the frequency of those features in the gene pool.
Positive or directional selection increases the frequency of a beneficial mutation, or pushes the mean in either direction.
en.wikipedia.org /wiki/Evolution   (9983 words)

 Evolution - Facts, Information, and Encyclopedia Reference article
Positive selection increases the frequency of a beneficial mutation.
Directional selection favors one extreme of a characteristic; results in a shift in the mean in the direction of the extreme.
It is understood that an organism's DNA sequence, in the absence of selection, undergoes a steady accumulation of neutral mutations.
www.startsurfing.com /encyclopedia/e/v/o/Evolution.html   (3970 words)

 Directional selection - Wikipedia, the free encyclopedia
In population genetics, directional selection (sometimes referred to as positive selection) occurs when natural selection favors a single allele and therefore allele frequency continuously shifts in one direction.
It stands in contrast to balancing selection where selection may favor multiple alleles, or purifying selection which removes deleterious mutations from a population.
A common example is the evolution of the peppered moth, where the favored direction has noticeably shifted in relation to the effects of humans.
en.wikipedia.org /wiki/Positive_selection   (118 words)

 positive selection
The implication of "strong positive selection" is that these new, variant forms of the genes gave great survival advantages to the humans that bore them.
Soranzo et al.: "Positive selection on a functional allele of the TAS2R16 bitter taste receptor associated with higher sensitivity to ß-glucopyranosides...
After positive selection mediated by CD1d-expressing cortical thymocytes, the mature NKT cell lineage undergoes a series of changes suggesting antigen priming...
www.mongabay.com /igapo/biotech/positive_selection.html   (408 words)

 The false positive selection induced by saturated sequence divergences
The false positive selection induced by saturated sequence divergences Feng Wang, Yasuhiko Wada (wangfeng@cc.saga-u.ac.jp ywada@cc.saga-u.ac.jp) Faculty of Agriculture, Saga University, Saga, 840-8502, Japan BIRD, Japan Science and Technology Agency, Tokyo, 102-8666, Japan To detect the positive selection is of special interest in the studies of phylogenetics and evolution.
The positive selection evidences are very useful to understand the evolutionary changes of genes and the molecular adaptation to the changes environment and functional constraints.
Among two available methods for detecting positive selection, the approximate (distance-based) method are thought to be conservative and reliable, while the likelihood-based method are thought to liberal and unreliable, because the models are easily to be violated in the real biological sequences.
www.iscb.org /ismb2004/posters/wangfengATcc.saga-u.ac.jp_518.html   (840 words)

 Brainstorms: Ka/Ks and positive selection
Positive selection produces the opposite effect of natural selection so far as Ka/Ks ratios are concerned and, thus, run counter to predictions made under Darwinism, but are exactly would ID would predict.
If natural selection is instead favoring the improvement of a new function, for say a duplicated gene, then of course mutations improving that new function (which must be nonsynonymous by definition) will on average be selected, and on average spread through the population to fixation.
The high Ka/Ks ratios are labeled 'positive selection' but nowhere can I find an explanation of how it can occur other than references to an 'extraordinary degree of evolutionary plasticity', 'adaptive evolution', 'bursts of rapid positive selection' and a correlation between high ratios and gene duplication.
www.iscid.org /boards/ubb-get_topic-f-6-t-000033-p-1.html   (4682 words)

 Two distinct pathways of positive selection for thymocytes.
Most mouse thymocytes undergoing positive selection are found on one of two pathways; the c-Kit+ and the c-Kit- pathways.
The rare DPhic-Kit- blast cells that thus are salvaged for positive selection by expressing a self-major histocompatibility complex selectable TCRalpha/beta up-regulate IL-7R, but not c-Kit, and are the principal progenitors on the c-Kit- pathway; this c-Kit-IL-7R+ pathway is mainly CD4 lineage committed.
In this view, positive selection on the c-Kit- path results from a salvage of cells that failed positive selection on the c-Kit+ path.
www.aegis.com /aidsline/1998/jun/M9861507.html   (419 words)

 Dienekes' Anthropology Blog: Recent positive selection in humans
Yet another study on positive selection in modern humans; you can find many many more by searching for "recent selection" or "positive selection" via the site search on the right sidebar.
Many of these instances of selection may reflect the pressures that came to bear as people abandoned their hunting and gathering way of life for settlement and agriculture, a transition well under way in Europe and East Asia some 5,000 years ago.
An important type of selective pressure that has confronted modern humans is the transition to novel food sources with the advent of agriculture and the colonization of new habitats [19,21].
dienekes.blogspot.com /2006/03/recent-positive-selection-in-humans.html   (1036 words)

 Frequent False Detection of Positive Selection by the Likelihood Method with Branch-Site Models -- Zhang 21 (7): 1332 ...
Positive selection for the foreground branch was inferred for
with the absence of positive selection for the purpose of estimating
False positive selection identified by ML-based methods: examples from the Sig1 gene of the diatom Thalassiosira weissflogii and the tax gene of a human T-cell lymphotropic virus.
mbe.oxfordjournals.org /cgi/content/full/21/7/1332   (4480 words)

 Positive Selection of CD4+ T Cells Is Induced In Vivo by Agonist and Inhibited by Antagonist Peptides -- Kraj et al. ...   (Site not responding. Last check: 2007-11-02)
Positive Selection of CD4+ T Cells Is Induced In Vivo by Agonist and Inhibited by Antagonist Peptides -- Kraj et al.
positive selection or induce negative selection (30) (31).
We have induced positive selection of transgenic thymocytes
www.jem.org /cgi/content/full/194/4/407   (5706 words)

 Patterns of Positive Selection in the Complete NBS-LRR Gene Family of Arabidopsis thaliana -- Mondragón-Palomino ...
The location of positively selected residues is important for inferring gene function.
The positions in which positive selection was detected are in bold and the sites that are part of the E
Polymorphism in abalone fertilization proteins is consistent with the neutral evolution of the egg's receptor for lysin (VERL) and positive Darwinian selection of sperm lysin.
www.genome.org /cgi/content/full/12/9/1305   (6270 words)

 Positive Darwinian selection drives the evolution of several female reproductive proteins in mammals -- Swanson et al. ...
Positive Darwinian selection drives the evolution of several female reproductive proteins in mammals -- Swanson et al.
Rapid evolution driven by positive Darwinian selection is a recurrent theme in male reproductive protein evolution.
positive selection acting on the female receptor (25) and was
www.pnas.org /cgi/content/full/98/5/2509   (3843 words)

 Positive selection on the human genome -- Vallender and Lahn 13 (Supplement 2): R245 -- Human Molecular Genetics
Zhang, J. and Nei, M. (2000) Positive selection in the evolution of mammalian interleukin-2 genes.
Podlaha, O. and Zhang, J. (2003) Positive selection on protein-length in the evolution of a primate sperm ion channel.
Civetta, A. (2003) Positive selection within sperm–egg adhesion domains of fertilin: an ADAM gene with a potential role in fertilization.
hmg.oxfordjournals.org /cgi/content/full/13/suppl_2/R245   (6905 words)

 Meiotic drive - EvoWiki   (Site not responding. Last check: 2007-11-02)
TT homozygotes have normal long tails; Tt heterozygotes have short tails and transmit ~ 90% of the t allele to their sperm; tt homozygotes are sterile.
Meiotic drive will increase frequency of the t allele to point where that become frequent enough to occur as tt homozygotes with appreciable frequency, whereupon selection works against t alleles.
This shows two levels selection: positive selection for t haplotypes at the level of the gene, negative selection for tt individuals at the level of the genotype (organism).
wiki.cotch.net /index.php/Meiotic_drive   (136 words)

 A Genomics Approach to the Detection of Positive Selection in Cattle: Adaptive Evolution of the T-Cell and Natural ...
was subject to positive selection during the evolution of a
predicted to be subject to positive selection (false positives).
Note that all but two of the sites under positive selection are located in the extracellular domain of CD2.
www.genetics.org /cgi/content/full/170/3/1189   (3468 words)

 Brainstorms: Ka/Ks and positive selection
Once the evolution of the paralogue has gone far enough to begin to achieve a new, positive function, albeit poorly, then natural selection will cut in and begin to restrict the non-synonymous substitutions while letting the synonymous substitutions proceed, as the paralogue is optimized to the new function through natural selection.
In regions of flat, folding sequence space, beta is zero, natural selection has nothing to work with, and the trajectory is essentially a random walk.
So there is a limit, so far as natural selection is concerned, as to how much guidance can be given to the evolving paralogue before it falls into non-folding, non-functional sequence space.
www.iscid.org /boards/ubb-get_topic-f-6-t-000033-p-2.html   (5630 words)

 Accuracy and Power of Bayes Prediction of Amino Acid Sites Under Positive Selection -- Anisimova et al. 19 (6): 950 -- ...
Bush R. Fitch, C. Bender, N. Cox, 1999 Positive selection on the H3 hemagglutinin gene of human influenza virus A Mol.
Fares M. Moya, C. Escarmis, E. Baranowski, E. Domingo, E. Barrio, 2001 Evidence for positive selection in the capsid protein-coding region of the foot-and-mouth disease virus (FMDV) subjected to experimental passage regimens Mol.
Peek A. Souza, L. Eguiarte, B. Gaut, 2001 The interaction of protein structure, selection, and recombination on the evolution of the type-1 fimbrial major subunit (fimA) from Escherichia coli J. Mol.
mbe.oxfordjournals.org /cgi/content/full/19/6/950   (5028 words)

 Detecting positive selection in Polynesians
We are interested in the genetic ancestry of human populations and detecting events of natural selection in human migration history.
These biological adaptations may be a result of selection for a “thrifty genotype”, a hypothesis originally proposed by James V. Neel to explain adaptation to periodic famine.
Therefore, the thrifty genotype hypothesis is of particular interest as it can provide insight into the search for candidate genes for positive selection in Polynesians.
www.eva.mpg.de /genetics/files/detecting.html   (210 words)

 Introns 1   (Site not responding. Last check: 2007-11-02)
Since members of many bacterial species appeared to be under intense pressure to streamline their genomes to facilitate rapid replication, if it were possible they would have dispensed with any preexisting introns and/or would have been reluctant to acquire them.
In this case the negative selection of individuals because of impaired stem-loop forming ability, would have been greater than the negative selection resulting from impaired protein function.
Regions where the constraints of classical Darwinian negative and positive selection, or of the encoding of overlapping genes, would not permit accommodation of DNA stem-loop potential, would be expected to be rich in introns.
mail.queensu.ca /~forsdyke/introns1.htm   (4321 words)

 Positive Selection   (Site not responding. Last check: 2007-11-02)
Proteins may evolve, in part, by positive selection.
will be much greater than 1.0, and positive selection is concluded.
That within species selection is usually negative, while between species selection appears to be positive in at least some instances, suggests that constraints may be episodic.
opbs.okstate.edu /~melcher/PE/PE33.html   (206 words)

 Galaxy: A platform for interactive large-scale genome analysis -- Giardine et al. 15 (10): 1451 -- Genome Research
Genes are labeled and have exons as boxes and introns as lines with arrowheads pointing in the direction of transcription.
The results of chromatin immunoprecipitations (ChIP data) are plotted as the negative log of the p-value, ranging in the vertical direction from 0 to 10.0 and with a continuous thin line placed at the threshold of 2.0.
Positions of repeats identified by RepeatMasker (A.F.A. Smit and P. Green, unpubl., http://ftp.genome.washington.edu/RM/RepeatMasker.html
www.genome.org /cgi/content/full/15/10/1451   (2679 words)

 Viruses and Other Gene Transfer Mechanisms. by Brig Klyce
3 May 2006: Genes undergo rapid mutation and selection immediately after transfer, according to biologists at McMaster University.
Focus on Horizontal Gene Transfer — a selection of recently published Reviews, Perspectives and Research Highlights on the topic of HGT from the Nature Reviews journals....
"Horizontally acquired sequences can be fixed in a population only when they confer a substantial selective advantage onto the recipient and therefore are subject to strong positive selection....
www.panspermia.com /virus.htm   (8586 words)

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