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Topic: Mutational meltdown

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Richard Dawkins

	Mutational meltdown - Biocrawler (Site not responding. Last check: 2007-10-30)
		Mutational meltdown refers to the process by which a small population accumulates deleterious mutations, which leads to loss of fitness and decline of the population size, which leads to further accumulation of deleterious mutations.
		A population experiencing mutational meltdown is trapped in a downward spiral and will go extinct eventually.
		Mutation load and the survival of small populations.
	www.biocrawler.com /encyclopedia/Mutational_meltdown (94 words)

	NationMaster - Encyclopedia: Population genetics (Site not responding. Last check: 2007-10-30)
		Population genetics is the study of the distribution of and change in allele frequencies under the influence of the four evolutionary forces: natural selection, genetic drift, mutation, and migration.
		Population genetics was a vital ingredient in the modern evolutionary synthesis, its primary founders were Sewall Wright, J. In practice, there are two bodies of evolutionary theory that exist in parallel, traditional population genetics operating in the genotype space and the biometric theory used in plant and animal breeding, operating in phenotype space.
		The foundational discipline is population genetics which studies the distribution of and change in allele frequencies of genes under the influence of the four evolutionary forces: natural selection, genetic drift, mutation and migration.
	www.nationmaster.com /encyclopedia/Population-genetics (3392 words)

	US Bazaar.com : Encyclopedia Pages : Mutational meltdown
		Mutational meltdown refers to the process by which a small population accumulates deleterious mutations, which leads to loss of fitness and decline of the population size, which may lead to further accumulation of deleterious mutations due to inbreeding depression.
		A population experiencing mutational meltdown is trapped in a downward spiral and will go extinct if the phenomenon lasts for some time.
		Usually, the deleterious mutations would simply be selected away, but during mutational meltdown, the number of individuals thus suffering an early death is too large relative to overall population size so that mortality exceeds the birth rate.
	encyclopedia.us-bazaar.com /?title=Mutational_meltdown (203 words)

	- Darwinism and the Deterioration of the Genome -- TrueOrigin Archive
		The DNA coding strand or non-template strand mutations affect the germline, and the complement strand, also called the template strand, is used to produce the mRNA that is identical to the coding strand, except in mRNA where a uracil is used instead of a thymine.
		The paucity of clearly helpful mutations must be considered in context with the estimate that 2x1020 mutations that are required to produce the natural living world existing today and the number of animals that are speculated to have once existed.
		A missense mutation in the bovine MGF gene is associated with the roan phenotype in Belgian blue and shorthorn cattle.
	www.trueorigin.org /mutations01.asp (6584 words)

	Spartanburg SC \| GoUpstate.com \| Spartanburg Herald-Journal (Site not responding. Last check: 2007-10-30)
		Mutational meltdown refers to the process by which a small population accumulates deleterious mutations, which leads to loss of fitness and decline of the population size, which may lead to further accumulation of deleterious mutations due to inbreeding depression.
		A population experiencing mutational meltdown is trapped in a downward spiral and will go extinct if the phenomenon lasts for some time.
		Usually, the deleterious mutations would simply be selected away, but during mutational meltdown, the number of individuals thus suffering an early death is too large relative to overall population size so that mortality exceeds the birth rate.
	www.goupstate.com /apps/pbcs.dll/section?category=NEWS&template=wiki&text=Mutational_meltdown (145 words)

	Philipp's Homepage: Evolution of sex
		Reviewed here are the DNA damage-repair hypothesis; simultaneous fixation of several favourable mutations at different loci; purging of deleterious mutations and Muller's ratchet or mutational meltdown; ecological hypotheses about heterogeneity in space and time, sibling competition, and diversification as a habitat becomes saturated with species; and the parasite-host coevolution hypothesis.
		This process, tending towards extinction of the asexual population, is termed mutational meltdown (Lynch et al.
		Mutation rates, recombination rates and which kind of sexual or asexual scheme is being followed all can change given the right conditions, and the concept of natural selection, though possibly given a different name, becomes recognisable as a universal function linking all kinds of complex adaptive systems.
	www.philippwesche.org /2004/writing/es.html (2706 words)

	The Proper Study Of Mankind: Why Sex Is Good (and not for the obvious reasons)
		One strong contender is the ‘mutational deterministic hypothesis’, devised by Alexey Kondrashov (2), and it is this model that the current paper in Nature draws on.
		The basic idea of the mutational deterministic hypothesis is that sex can bring harmful mutations present in two parents together in a single individual; if this individual then dies, this eliminates harmful mutations (deleterious mutations, in the argot of geneticists) from the population.
		Mutational robustness, or insensitivity to mutations, is a capacity to dampen down the harmful effects of mutations.
	psom.blogspot.com /2006/03/why-sex-is-good-and-not-for-obvious.html (3226 words)

	Mutational Meltdown (Site not responding. Last check: 2007-10-30)
		It has long been known that random mutations occur quite frequently, and that the majority of mutations are harmful, but biologists have not agreed on the extent to which mutations or other genetic factors might contribute to extinction.
		This snowballing process is known as mutational meltdown.
		For simple systems, such as the buildup of mutations in asexual populations, it is possible to develop analytical models in the form of math ematical equations that predict the number of generations to extinction as a function of the mutation rate, the aver age effect of each mutation, and other genetic variables.
	www.csi.uoregon.edu /projects/mm (471 words)

	2.10 Mutational Meltdown
		During this period the population becomes less and less healthy, since on average mutations are slightly harmful and when a mutation is fixed it becomes part of every individual in the population.
		This phenomenon is known as a mutational meltdown.
		A plot that shows the progress of the buildup of mutations and their effect on an example population is shown in Figure 2.
	www.ipp.mpg.de /de/for/bereiche/stellarator/Comp_sci/CompScience/csep/csep1.phy.ornl.gov/mu/node12.html (631 words)

	BioMed Central \| Full text \| Quasispecies theory in the context of population genetics
		In the formation of a quasispecies, the population minimizes the mutational load by accumulating sequences that have a reduced probability to suffer from deleterious mutations [27,28,39,40].
		Since for many RNA viruses the genomic mutation rate is already on the order of one [48,49], even moderately large populations of RNA viruses, or populations that undergo regular bottlenecks, are candidates for quasispecies behavior.
		Mutational meltdown will operate in any fitness landscape, as long as the population size is sufficiently small, the mutation rate sufficiently large, or the hard selection pressure sufficiently strong.
	www.biomedcentral.com /1471-2148/5/44 (5272 words)

	Meltdown Rrsp
		Ice Age 2: The Meltdown DS Their world is melting, and your Ice Age 2 The Meltdown pals need help escaping the biggest flash flood in prehistory.
		Ice Age 2: The Meltdown PC Their world is melting, and your Ice Age 2 The Meltdown pals need help escaping the biggest flash flood in prehistory.
		Nuclear meltdown - A nuclear meltdown occurs when the core of a nuclear reactor melts, and is generally considered a serious nuclear accident.
	mu17.mfedbank.com /meltdownrrsp.html (382 words)

	Virus Evolution Workgroup: 1999 Workshop Abstract
		Thus, low mutation rates seem not to be the cause for low genetic diversity in plant virus populations.
		Mutational meltdown may also occur in nature and have an important role in virus evolution.
		A mutation in tomato aspermy cucumovirus that abolishes cell-to-cell movement is maintained to high levels in the viral RNA population by complementation.
	www.noble.org /virusevolution/abstracts/Garcia-Arenal.htm (1595 words)

	NOAA/NMFS/NWFSC-TM30: Inbreeding Depression and Outbreeding Depression
		We know from empirical results from several organisms that deleterious mutations, mild as they may be in their individual effects, appear at a fairly high rate.
		A rule of thumb is that, in small populations, new, mildly deleterious mutations will accumulate in the population at a rate that is half the mutation rate at the genomic level.
		Also keep in mind that even if all deleterious mutations have been purged, they will eventually return to the population, because the per individual mutation rate to deleterious genes is about one per generation.
	www.nwfsc.noaa.gov /publications/techmemos/tm30/lynch.html (4479 words)

	Mutational meltdown - the free encyclopedia (Site not responding. Last check: 2007-10-30)
		Mutational meltdown refers to the process by which a
		small population accumulates deleterious mutations, which leads to loss of
		fitness and decline of the population size, which leads to further accumulation of deleterious mutations.
	www.free-web-encyclopedia.com /default.asp?t=Mutational_meltdown (67 words)

	Su Journal » Blog Archive » Meltdown
		A nuclear meltdown occurs when the 2006 in Camp Hill, Pennsylvania by Bill Frist was calling late Weduc night and I expanded a data breach can be slipping into a new study shows that came to be properly A vote on nominee William Myers may be.
		Internet Meltdown Add to Bypass and Otherwise Deal With interest rates and screenshots from hyperactive adolescence to be slowly accelerating as the allegations and everyone in the post on individual liberty, limited government, free markets and what is happening with this years Meltdown is known as mutational meltdown.
		Meltdown BBS is a clear and present danger, Supreme Court justiceuc homework strugglesuc of recent currency reforms, analysts warn country faces absolute collapse.
	sujornal.com /2006/11/29/meltdown (867 words)

	Touchstone Archives: The Book of Life: Revised Edition
		According to the laws of inheritance, if both parents have two copies of the damaged gene, their offspring must be mutated, yet they often produce perfectly normal offspring.
		Without mutations we would all certainly be dead (or, at least, unborn) for a system that copies itself precisely cannot move forwards.
		If mutations inexorably cause genomic information to degenerate, in the manner of manuscript copying mistakes, then to rely upon similar mistakes to create vast new kinds and amounts of functional information is to presuppose what may seem to be a prodigious series of naturalistic miracles.
	www.touchstonemag.com /archives/article.php?id=18-08-012-c (1289 words)

	Genetic Drift
		Because its effects are the greatest in populations of small size, they are always subject to ‘mutational meltdown’ or accumulating deleterious mutations resulting in the decrease of the fitness of the population and thus even further accumulating more deleterious mutations.
		Such a mutational meltdown most of the time ends in the extinction of the species.
		When genetic drift is strong, deleterious mutations may accumulate, leading to an irreversible decline in population fitness.
	www.freewebtown.com /bhaktivedanta108/3_Genetic_Drift.html (1654 words)

	Behavior OnLine Forums - View Single Post - Selling Evolution
		We could in principle predict which/when/where mutations would happen if we knew the exact state of every particle in the universe and were able to model their future dynamics (in practice, of course, this kind of predictive power is beyond reach).
		What I really meant by "random" is that mutations occur without regard for their effect upon the adaptive design of organisms (with a few exceptions that prove the rule, but I won't go into them).
		Deleterious mutations are thus expunged from the population.
	www.behavior.net /bolforums/showpost.php?p=4030&postcount=12 (385 words)

	Fathom :: The Source for Online Learning
		Mark Ridley, lecturer in the department of zoology at Oxford University, argues that the evolution of complex life presents a series of problems to the evolutionary theorist.
		"Mutational Meltdown" a term developed to describe the replication of errors throughout a reproductive lineage, is one of these challenges.
		In this lecture for the Darwin@LSE lecture series, Ridley explains mutational meltdown through the analogy of the children's game, "Chinese whispers" or "rumours," whereby a message is repeated down a line of children, only to have been laughably corrupted by the time it has reached the end of the line.
	www.fathom.com /feature/122410/index.html (206 words)

	Short-term threats to persistence
		Still another approach is to assume that the deleterious effects noted in these small populations is primarily the result of the expression of recessive deleterious alleles.
		The expected time to extinction increases rapidly in mutational meltdown models such that in populations with an effective size greater than a few hundred persistence times are well into the hundreds or thousands of generations (4).
		Mutational parameters are close to those estimated for Drosophila melanogaster: genomic mutation rate = 1.5, selection coefficient against recessive homozygotes = 0.015, dominance coefficient = 0.35.
	darwin.eeb.uconn.edu /eeb310/lecture-notes/genetics/node8.html (713 words)

	2.10 Mutational Meltdown (Site not responding. Last check: 2007-10-30)
		The meltdown can be explained as follows: when the critical point has been reached, the population has enough fixed mutations (as well as segregating mutations) so that barely enough individuals survive to fill the population up to the carrying capacity of the environment.
		However, due to breeding pressure they are now selected for mating, and they pass their mutations to their children.
		Since their children are, on average, even less healthy, this new generation may not be large enough to fill the carrying capacity.
	www.phy.ornl.gov /csep/CSEP/MU/NODE12A.html (343 words)

	Genetic Drift and Evolution - ResearchID.org
		This is why the small populations of endangered species are especially subject to what is called mutational meltdown or accumulations of deleterious mutations that results in decreasing the fitness of the population and thus further accumulation of even more deleterious mutations.
		Such a mutational meltdown most of the time ends in extinction of the species.
		The bottom line of Haldane’s dilemma is that selection to fix new beneficial mutations occurs at glacial speeds, and the more nucleotides which are under selection, the slower the progress.
	www.researchintelligentdesign.org /wiki/Genetic_Drift_and_Evolution (1356 words)

	JSMF - Studying Complex Systems: 2006 Research Awards
		This project addresses two important factors that contribute to ability of a pathogen to evolve: the mutations that fuel its evolution and the host conditions that force it to evolve.
		From our perspective, forecasting such mutations can be the key to developing effective controls—both vaccines that can withstand pathogen evolution and antiviral therapies that, by increasing the frequency of mutations, cause a mutational meltdown of the virus.
		To better understand the spectrum of mutations that drive evolution and the puzzling differences in the evolutionary propensities of viruses, we will build biologically realistic models of the mutational networks that underlie the evolution of ribonucleic acid (RNA) molecules.
	www.jsmf.org /grants/cs/essays/2006/meyers.htm (1276 words)

	Meltdown in TutorGig Encyclopedia
		Meltdown may be Nuclear meltdown, the melting of the core of a reactor Meltdown comics, a female comicbook character Meltdown, a short lived monthly anthology title published by Marvel UK, reprinting..
		Meltdown is the name of several album s by year Meltdown Steve Taylor album Meltdown, a 1984 album by Steve Taylor.
		Mutational meltdown refers to the process by which a Small population size small population accumulates...
	www.tutorgig.com /es/Meltdown (811 words)

	Accumulation of Deleterious Mutations in Small Abiotic Populations of RNA -- Soll et al. 175 (1): 267 -- Genetics
		Mutations in the CE system are generated by the protein enzymes.
		In this lineage, the immunity mutation arises in about burst 15 and is rapidly fixed in the population by burst 21.
		The insurance mutation arises later, around burst 20, and slowly accumulates to fixation around burst 43 (not shown on gel).
	www.genetics.org /cgi/content/full/175/1/267 (4538 words)

	Return home
		It is typically assumed mutation rates are constant but there is little empirical data to justify this assumption.
		She is also working on experiments attempting to determine whether mutation rates are condition-dependent.
		At the moment, she is attempting to compare the rate of sex-linked lethal mutations in fruit flies in high- vs. low-condition.
	www.zoo.utoronto.ca /afagrawal/labbies (432 words)

	vsevcosmos: The risk of extinction - the mutational meltdown or the overpopulation. [q-bio.PE/0607045]
		The phase diagrams survival-extinction for the Penna model with parameters: (mutations rate)-(birth rate), (mutation rate)-(harmful mutations threshold), (harmful mutation threshold)-(minimal reproduction age) are presented.
		The extinction phase may be caused by either mutational meltdown or overpopulation.
		When the Verhulst factor is responsible for removing only newly born babies and does not act on adults the overpopulation is avoided and only genetic factors may lead to species extinction.
	vsevcosmos.livejournal.com /19183094.html (110 words)

	Evolution of sex: theory
		Consistent with the results of May and Anderson (1983), we find that host-parasite coevolution is NOT sufficient by itself to prevent the replacement of a sexual population by a clonal lineage, unless the parasites kill or castrate infected hosts (Howard and Lively 1994).
		We also find that mutation accumulation is not sufficient, assuming that clones do not begin in mutation-selection balance (as assumed in some models), but rather are sampled from the distribution of mutations in the sexual population, which is at mutation-selection balance (Howard and Lively 1998).
		However, we find that the combination of mutation accumulation and host-parasite coevolution is a powerful mechanism for the elimination of clones in the short term, and the evolutionary persistence of sexual reproduction (Howard and Lively 1994, 1998).
	www.indiana.edu /~curtweb/Research/sex&recomb.theory.html (546 words)

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