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Topic: Back mutation

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	[No title]
		Mutations are usually modifications of existing genes rather than totally new characteristics.
		Instead an equilibrium will be reached such that the number of dominate alleles mutating to recessive alleles equals the number of recessive alleles that mutate back to dominate.
		If selection pressure against an allele is less than the rate of mutation that produces it, the mutation will spread through the population even though it is detrimental to the individuals with it.
	www.gwu.edu /~darwin/BiSc150/PopGen/Mutation.htm (1222 words)

	Progressive reversion of HIV-1 mutations may have serious consequences
		However, "reversions of a second (RT) mutation and 3 PR mutations were associated with an increase in viral replicative capacity and this was temporally correlated with a marked decrease in CD4 cell number," the researchers report.
		However, reversions of a second RT mutation and 3 PR mutations were associated with an increase in viral RC, and this was temporally correlated with a marked decrease in CD4 cell number.
		The reversion of particular mutations appeared to be associated with an increase in viral RC, which implies that virus evolution to improve replication occurred in the absence of antiretroviral drugs.
	www.natap.org /2004/jan/010504_08.htm (2791 words)

	Mutation, Mutagens, and DNA Repair
		Mutations, or heritable alterations in the genetic material, may be gross (at the level of the chromosome, which we have already discussed) or point alterations (this technically means mutations not visible as cytological abnormalities and/or those which map to a single "point" in experimental crosses).
		Missense mutations may have very serious consquences, as in the case of sickle-cell anemia, mild consequences as in the case of hemoglobin C (a different amino acid substitution in position 6 of beta-globin) or no phenotype as in the case of two known amino acid substitutions at position 7 of beta-globin.
		Mutator mutants have since been isolated in other organisms and have been shown to affect various components of the DNA replication complex; alterations in a number of these proteins are likely to affect the accuracy of the system.
	www-personal.ksu.edu /~bethmont/mutdes.html (4992 words)

	Evolution: Library: Double Immunity
		O'Brien hypothesizes that this mutation, dating back 700 years, may have been a selective advantage during the bubonic plague, as it is today, with the onslaught of HIV.
		Logically, the mutation must have occurred in the past, acting as a defense against a different, previous epidemic caused -- like the AIDS epidemic -- by a pathogen that also targeted white blood cells.
		At present, scientists are trying to infect such resistant cells with bubonic plague bacteria to test the hypothesis that the mutation in the CCR-5 receptor gene could have thwarted the plague in the Middle Ages, as it does HIV today.
	www.pbs.org /wgbh/evolution/library/10/4/l_104_05.html (505 words)

	Prevalence of Antiretroviral Drug Resistance Mutations in Chronically HIV--Infected, Treatment-Naive Patients: ...
		The results indicate that prevalence of mutations conferring antiretroviral resistance in chronically infected patients is common (10.8%) and that genotypic resistance testing of chronically infected patients before initiation of therapy may be appropriate.
		Mutations at the 215 position of reverse transcriptase (RT), which have been associated with resistance to thymidine analogues, were also frequently seen (14 samples), as well as were revertants from 215Y, the most common 215 mutation associated with thymidine analogue resistance.
		By drug class, the estimated prevalence of mutations conferring resistance to nucleoside reverse-transcriptase inhibitors was 7.8%, and the prevalence was 3.0% for nonnucleoside reverse-transcriptase inhibitors and 0.7% for protease inhibitors.
	www.natap.org /2005/HIV/020205_08.htm (2938 words)

	The Rate of Compensatory Mutation in the DNA Bacteriophage {phi}X174 -- Poon and Chao 170 (3): 989 -- Genetics
		a compensatory mutation, we sequenced an interval of the genome
		2.— Plot of the observed proportion of replicate populations that independently acquire a compensatory mutation, instead of the back mutation, as a function of the log-transformed relative fitness of the deleterious mutation.
		mutagenesis to revert the deleterious mutation in an arbitrary
	www.genetics.org /cgi/content/full/170/3/989 (6001 words)

	Organismal Biology/Physiology Thread - Student Doctor Network Forums
		With regards to mutations, i would assume that the three (and i would call them three, they're all pretty distinct) TPR "classes" of mutations are going to be the most common fodder for questions asked.
		Point mutations are single base changes and can be neutral (do not change the amino acid being coded for), missense (the amino acid being coded for is changed to another amino acid due to the point mutation) or nonsense (the amino acid being coded for is changed to a "stop" due to the point mutation).
		Back mutations: When something was once A but is now B changes “back” to A again.
	forums.studentdoctor.net /showthread.php?t=207484 (2040 words)

	Equations (Site not responding. Last check: 2007-10-10)
		But if the proportion of migrants is low, or if allele proportions are similar in residents and migrants, the effect of gene flow may be more similar to that of mutations (an occasional source of alternate allele).
		Mutation is not considered an important force in changing allele proportions.
		The importance of mutations is as a source of alternative alleles, some of which might become abundant in a population due to genetic drift or to selection.
	csciwww.etsu.edu /popgen99se/forces.htm (623 words)

	Dr. Lee Spetner's continued exchange with Dr. Edward E. Max
		Thus, for a mutation to qualify as a representative member of the required multitude of long series that are supposed to produce evolution, it must bring new information not just to the genome of the organism, but the information must be new to the entire biocosm.
		Thus, for example, a mutation that disables a repressor gene causing a constitutive synthesis of an enzyme might be advantageous to an organism under special circumstances, but the disabling of a gene does not represent the mutations required by the theory.
		Indeed, both the rate and predominant mechanism of mutation may be different in different species of organisms, depending on whether they have more or less exposure to cosmic rays and other environmental mutagens, and depending on the nature and robustness of their genomic error-correction mechanisms.
	www.trueorigin.org /spetner2.asp (17052 words)

	[No title]
		An rII mutant, #M-067, was treated with the mutagen proflavine in an attempt to induce reverse mutation to the wild-type r+.
		Mutant B most likely has a frameshift mutation (loss or gain of a bp) close to the beginning of the coding sequence which 'scrambles' the codons from this point on and generates a stop codon at codon 360.
		'Nonsense mutations' is a term describing a property (produces a non-scheduled stop codon) of a mutation not a description of a mechanism as previously.
	www.rpi.edu /locker/53/001053/CHAP12DAT (1392 words)

	1
		Let p be the frequency of the presence of the intron and q be the frequency of its absence.
		This makes sense, because the rate of mutation making a is faster than the rate of mutation turning it back into A. (Try to always check your answers in this common sense, qualitative kind of way).
		Suppose there is no back-mutation -- only forward mutation (A to a) at the rate given in #3 -- and A is 10% more fit than a.
	www.columbia.edu /cu/biology/courses/c3020/solutions-1.html (2433 words)

	Mutation
		Assume that mutations occur while gametes are in gamete pool (after shedding, before fusion)
		Because selection and mutation are opposing forces, they balance each other to create an equilibrium
		Again, when selection is strong and mutation rate is low, equilibrium frequency of mutant allele is low
	ib.berkeley.edu /courses/ib162/Mutation.htm (479 words)

	The correct answer is in blue:
		The mutation is more occurs in either population by chance, but would tend to be a recurring mutation with little to no back mutation in the population that lives in the acidic bog.
		Back mutations would be rare in the spruce population that lives in the acidic bog.
		Mutation rate from H to h will increase because of the lack of breeding between HH and Hh individuals.
	www.gwu.edu /~darwin/BiSc150/Exam1_2005_Key.htm (3436 words)

	Forward and Reverse Mutation (Site not responding. Last check: 2007-10-10)
		Mutations from a normally functioning reference gene, chormosome, or organism to a mutant condition are called forward mutations.
		Their reversal by a new mutation that restores the original DNA sequence is called back mutation or reversion.
		In addition, new mutations at a site distinct from a forward mutation can sometimes restore the nonmutant phenotype; these are called suppressor mutations, because it suppresses the effects of the first mutation.
	expage.com /forwardnreverse (90 words)

	EvolvingCode.net - mutation (Site not responding. Last check: 2007-10-10)
		Mutation is any alternation of the nucleotide base sequence.
		Mutation affects genotype and selection operates on phenotype.
		Mutation happens independently from the fitness of phenotype.
	www.evolvingcode.net /index.php?page=mutation (79 words)

	Molecular Evolution C3020
		mutations per generation and the mutation rate from a to A is 0.47 * 10
		In a haploid organism, with the same mutation rate, what is the expected equilibrium frequency of a?
		Suppose there is no back-mutation -- only foreward mutation (A to a) at the rate given in #3 – and A is 10% more fit than a.
	www.columbia.edu /cu/biology/courses/c3020/3020-problems1.html (957 words)

	Re: can environmental variables induce visible mutations in fruit flies
		If a mutation is very rare, it can be almost impossible for a single researcher to find it by looking at wild-type flies that have been exposed to strong mutatenic agents such as radiation or mutagenic chemicals.
		So, for example looking for the curly wing mutation: http://www.exploratorium.edu/exhibits/mutant_flies/curly-wings.gif even though this mutation is dominant, (only one copy of the gene needs to be mutated), starting with wild flies, is difficult.
		So if the normal mutation rate of curly to wild-type is one in 100,000 the mutation rate at the high temperature might go up to one in 50,000 or something like that.
	www.madsci.org /posts/archives/Mar2003/1047321968.Ge.r.html (670 words)

	Mutations (Site not responding. Last check: 2007-10-10)
		Mutations are changes in the genotype which may or may not affect the phenotype
		The amino acid substitution induced by the missense mutation may have no effect on its function OR It may abolish the activity of the protein or alter its function having an effect on phenotype
		Mutation rate is the probability that a gene will mutate when the cell divides
	microvet.arizona.edu /Courses/vsc610/mic205/mutations.html (632 words)

	Biotechterms.org
		The mutation alteration to the DNA sequence would alter its meaning, that is, its ability to produce the normal amount or normal kind of protein, so the (organism or cell) is itself altered.
		For example, during the eighteenth century, one orange tree in Brazil was discovered to be producing seedless oranges; as a result of a naturally-ocurring mutation in its DNA.
		If that particular mutation was of a single nucleotide in that orange tree's DNA (e.g., caused by ultraviolet radiation striking it), then it was a point mutation.
	biotechterms.org /sourcebook/saveidretrieve.php3?id=1268 (181 words)

	Mutation and DNA Repair
		Luria and Delbruk used what they called the "Fluctuation Test" to show that many mutations for phage T1 resistance were present in the culture before phage was added.
		Occur at sites different from the original mutation and mask or compensate for the initial mutation without reversing it.
		Short section of newly replicated DNA containing a mutation is removed and a new strand is re-synthesized using the template
	www.uvm.edu /~dstratto/bcor101/mutation.htm (567 words)

	Mutation rates: estimating phase variation rates when fitness differences are present and their impact on population ...
		Mutation rates: estimating phase variation rates when fitness differences are present and their impact on population structure -- Saunders et al.
		Mutation rates: estimating phase variation rates when fitness differences are present and their impact on population structure
		Stocker, B. Measurements of rate of mutation of flagellar antigenic phase in Salmonella typhimurium.
	mic.sgmjournals.org /cgi/content/full/149/2/485 (5998 words)

	Simulating pseudogene evolution in vitro: Determining the true number of mutations in a lineage -- Vartanian et al. 98 ...
		was evidence of back mutations because the lineage from R67 to
		Sites harboring back mutations are emphasized by the letter B. Sites 7 and 89 reveal series of pyrimidine transitions.
		On the ordinate are the true percentages of forward, back, and total mutations in the lineage to the intermediate sequence as well as the true percentage of variable sites.
	www.pnas.org /cgi/content/full/98/23/13172 (2325 words)

	Lady Gouldian Finch .com - Shopping - Gouldian Price List
		Green back of the Normal is replaced by yellow.
		Green back of the Normal is replaced by a teal blue in the Hens.
		In this mutation Black is Gray as in the Dilute Yellow-back mutation.
	www.ladygouldianfinch.com /pricelist.mgi (854 words)

	MUTATION 6'1m1f Evolution by mutation and natural selection
		If we don't have the same mutation, we wouldn't be the same species.
		The odds against someone being born with our mutation is billions to one.
		HIM -- (pulls back hood) HER -- (gasps) Well, I finally found someone uglier than me! Your face is almost as bald as mine!
	www.fea.net /Bobsnook/stg/tp/mutation.htm (838 words)

	Family Tree DNA Forum - R1b got messed up
		That I know of there are no types floating out there that have the M343 mutation but don't have the old P25 mutation (if I'm wrong correct me as it would trump everything I'm saying in this paragraph).
		For example, there's a branch in the C haplogroup that has like 10 or 12 mutations on it.
		If he comes back negative for M269 you might want to ask about M18 and M73 to rule out R1b1a and R1b1b.
	www.familytreedna.com /forum/showthread.php?p=15653 (1196 words)

	Family Tree DNA Forum - HVR2 match, different haplogroup?
		The bottom line is that you and someone else may match HVR1 and even HVR2 mutations, but if you are of different haplogroups, you are not related matrilineally within the last several thousand years.
		I hadn't thought about the possibility of a back mutation.
		The other scenario you mentioned might be it also given that the results came in almost a year apart.
	www.familytreedna.com /forum/showthread.php?t=2032 (290 words)

	POPULATION BIOLOGY NOTES SET
		represents the combination of forward and back mutations;
		Point mutations: thus far we have focused on them;
		• Since mutation rates are low – equilibrium frequency likely to be low with significant selection;
	faculty.schreiner.edu /fstevens/B3440N2.htm (987 words)

	Bleeding Disorders -2
		b.Resistance to activated Protein C (Factor V-Q506 ("Leiden") Mutation)
		c.The Leiden Mutation reduces ability of Protein C to cleave at one of the three sites
		b.Homozygous and heterozygous mutation predicts recurrent DVT in cancer patients [5]
	enotes.tripod.com /bleeding2.htm (629 words)

	H statistic
		Enter the frequencies of segregating sites of various types:
		Example: f1=3 f2=2 f3=1 f8=1 f9=1; where, for example, f1=2 means that the number of mutations of size 1 (externalmutations) is 2.
		The results of the H-statistic are now scaled by the variance of the statistic.
	www.genetics.wustl.edu /jflab/htest.html (150 words)

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