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| '''Allele frequency''', or '''gene frequency''', is the proportion of a particular [[allele]] (variant of a gene) among all allele copies being considered.
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| Formal definition: Allele or gene frequency is the percentage of all alleles at a given [[locus (genetics)|locus]] in a population [[gene pool]] represented by a particular allele.<ref>King R.C; Stansfield W.R. & Mullign P.K. 2006. ''Dictionary of Genetics''. 7th ed, Oxford University Press. p16; p174. ISBN 978-0-321-79578-6</ref><ref>Klug W.S; Cummings M.R; Spencer C.A. & Palladino M.A. ''Concepts of Genetics''. 10th ed, Pearson. p700{{ndash}}706, including worked examples.</ref>
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| In other words, it is the number of copies of a particular allele divided by the number of copies of all alleles at the genetic place (locus) in a [[population]]. It is usually expressed as a [[percentage]]. In [[population genetics]], allele frequencies are used to depict the amount of [[genetics|genetic]] diversity at the individual, population, and [[species]] level. It is also the relative proportion of all alleles of a gene that are of a designated type.
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| Given the following:
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| # a particular locus on a [[chromosome]] and the [[gene]] occupying that locus
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| # a population of ''N'' individuals carrying ''n'' loci in each of their [[somatic cell]]s (e.g. two loci in the cells of [[diploid]] species, which contain two sets of chromosomes)
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| # different alleles of the gene exist
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| # one allele exists in ''a'' copies
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| then the allele frequency is the fraction or percentage of all the occurrences of that locus that is occupied by a given allele and the frequency of one of the alleles is ''a/(n*N)''. | |
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| For example, if the frequency of an allele is 20% in a given population, then among population members, one in five chromosomes will carry that allele. Four out of five will be occupied by other variant(s) of the gene.
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| Note that for diploid genes the fraction of ''individuals'' that carry this allele may be nearly ''two in five'' (36%). The reason for this is that if the allele distributes [[random]]ly, then the [[binomial theorem]] will apply: 32% of the population will be [[heterozygous]] for the allele (i.e. carry one copy of that allele and one copy of another in each somatic cell) and 4% will be [[homozygous]] (carrying two copies of the allele). Together, this means that 36% of diploid individuals would be expected to carry an allele that has a frequency of 20%. However, alleles distribute randomly only under certain assumptions, including the absence of [[selection]]. When these conditions apply, a population is said to be in [[Hardy–Weinberg principle|Hardy–Weinberg equilibrium]].
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| The frequencies of all the alleles of a given gene often are graphed together as an ''allele [[frequency distribution]] [[histogram]]'', or ''[[allele frequency spectrum]]''. Population genetics studies the different "forces" that might lead to changes in the distribution and frequencies of alleles—in other words, to [[evolution]]. Besides selection, these forces include [[genetic drift]], [[mutation]] and migration.
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| == Calculation of allele frequencies from genotype frequencies==
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| The actual frequency calculations depend on the [[ploidy]] of the species for autosomal genes.
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| ===Monoploids===
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| The frequency of an allele ''a'' is the [[quotient]] of the number of copies of the allele and the population or sample size.
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| ===Diploids===
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| If <math>f(AA)</math>, <math>f(Aa)</math>, and <math>f(aa)</math> are the frequencies of the three genotypes at a [[locus (genetics)|locus]] with two alleles, then the frequency ''p'' of the A-allele and the frequency ''q'' of the a-allele are obtained by counting alleles. Because each homozygote AA consists only of A-alleles, and because half of the alleles of each heterozygote Aa are A-alleles, the total frequency ''p'' of A-alleles in the population is calculated as
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| :<math>p=f(\mathbf{AA})+ \frac{1}{2}f(\mathbf{Aa})= \mbox{frequency of A}</math>
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| Similarly, the frequency ''q'' of the a allele is given by
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| :<math>q=f(\mathbf{aa})+ \frac{1}{2}f(\mathbf{Aa})= \mbox{frequency of a}</math>
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| It would be expected that ''p'' and ''q'' sum to 1, since they are the frequencies of the only two alleles present. Indeed they do:
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| :<math>p+q=f(\mathbf{AA})+f(\mathbf{aa})+f(\mathbf{Aa})=1</math>
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| and from this we get:
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| :<math>q=1-p</math> and <math>p=1-q</math>
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| If there are more than two different allelic forms, the frequency for each allele is simply the frequency of its homozygote plus half the sum of the frequencies for all the heterozygotes in which it appears.
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| Allele frequency can always be calculated from [[genotype frequency]], whereas the reverse requires that the Hardy–Weinberg conditions of random mating apply. This is partly due to the ''three'' genotype frequencies and the ''two'' allele frequencies. It is easier to reduce from three to two.
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| ====An example population====
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| Consider a population of ten individuals and a given locus with two possible alleles, ''A'' and ''a''. Suppose that the [[genotype]]s of the individuals are as follows:
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| :''AA'', ''Aa'', ''AA'', ''aa'', ''Aa'', ''AA'', ''AA'', ''Aa'', ''Aa'', and ''AA''
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| Then the allele frequencies of allele ''A'' and allele ''a'' are:
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| :<math>p=prob_A=\frac{2+1+2+0+1+2+2+1+1+2}{2*10}=0.7</math>
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| :<math>q=prob_a=\frac{0+1+0+2+1+0+0+1+1+0}{2*10}=0.3</math>
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| so if a locus is chosen at random there is a 70% chance it will be the ''A'' allele, and a 30% chance it will be the ''a'' allele.
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| ===Polyploids===
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| ==Allele frequency dynamics==
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| The dynamics of allele and gene frequencies are affected by several factors such as migration, mutation, drift, population size, mating and others. The [[Hardy-Weinberg]] law describes an equilibrium for diploids genes. See details under [[population genetics]].
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| ==See also==
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| *[[Single-nucleotide polymorphism]]
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| * [[Allele frequency net database]]
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| == References ==
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| {{reflist}}
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| ==External links==
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| *[http://alfred.med.yale.edu/alfred/ ALFRED database]
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| *[http://www.ehstrafd.org EHSTRAFD.org - Earth Human STR Allele Frecuencies Database]
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| *[http://www.ehstrafd.org/download/vWA_17_A1.rar VWA 17 Allele Frequency in Human Population (Poster)]
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| *[http://www.allelefrequencies.net Allele Frequencies in Worldwide Populations]
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| {{cite journal |last=Cheung|first=KH |coauthors=Osier MV, Kidd JR, Pakstis AJ, Miller PL, Kidd KK |title=ALFRED: an allele frequency database for diverse populations and DNA polymorphisms |journal=Nucleic Acids Research |volume=28 |issue=1 |year=2000 |pages=361–3 |doi=10.1093/nar/28.1.361 |pmid=10592274 |pmc=102486 }}
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| {{cite journal |last=Middleton|first=D |coauthors=Menchaca L, Rood H, Komerofsky R |title=New allele frequency database: http://www.allelefrequencies.net |journal=Tissue Antigens |volume=61 |issue=5 |year=2002 |pages=403–7 |pmid=12753660 |doi=10.1034/j.1399-0039.2003.00062.x }}
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| {{MolecularEvolution}}
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| [[Category:Population genetics]]
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| [[Category:Genetic genealogy]]
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You can find easy techniques to accelerate computer by making the many out of the built in tools in your Windows plus downloading the Service Pack updates-speed up your PC plus fix error. Simply follow a few guidelines to quickly make the computer quick than ever.
So 1 day my computer suddenly began being strange. I was thus frustrated, because my files were missing, plus I cannot open the files that I needed, and then, suddenly, everything stopped working!
So what if you look for when we compare registry cleaners. Many of the registry products accessible today, have truly similar features. The principal ones which you need to be seeking are these.
It is regular which the imm32.dll error is caused due to a mis-deletion activity. If you cannot discover the imm32.dll anywhere on a computer, there is no doubt that it need to be mis-deleted whenever uninstalling programs or additional unneeded files. Hence, we can straight deal it from other programs or download it from a secure web plus then put it on a computer.
Another well-known cause of PC slow down is a corrupt registry. The registry is a important component of computers running on Windows platform. When this gets corrupted a PC will slowdown, or worse, not commence at all. Fixing the registry is easy with all the use of the system and registry reviver.
Another key element whenever you compare registry products is having a center to manage a start-up tasks. This just signifies to select what programs you want to begin when you commence the PC. If you have unwanted programs starting when you boot up your PC this may lead to a slow running computer.
Your registry is the spot all the significant configurations for hardware, software and user profile configurations plus preferences are stored. Every time 1 of these elements is changed, the database then begins to expand. Over time, the registry can become bloated with unnecessary files. This causes a general slow down however, in extreme situations may cause important jobs plus programs to stop working all together.
All of these difficulties is conveniently solved by the clean registry. Installing the registry cleaner allows you to utilize a PC without worries behind. You may capable to utilize you program without being afraid that it's going to crash inside the center. Our registry cleaner will fix a host of errors on your PC, identifying lost, invalid or corrupt settings in your registry.