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23-606: IC2 may refer to: IC2, one of the British police's radio IC codes Intercity 2 , railway service by Deutsche Bahn IC2 (Portugal) , see Roads in Portugal Interdisciplinary Consulting Corporation , an aerospace sensor company in Florida, USA [REDACTED] Topics referred to by the same term This disambiguation page lists articles associated with

46-455: A " Stop and Search " or arrest), in addition to visual assessment police are also required to use the more extensive "18+1" self defined ethnicity codes, "even if the category chosen is clearly at odds with the officer's visual assessment". The usage of IC codes in relation to individuals is recorded as part of information collected during activities including "Stop and Search", issuing of fixed penalties, arrest, and custody of individuals, and

69-540: A regular basis. The IC classification has also been used in scientific research. In 2014, a global forensic database based on the codes was established. It contains the DNA microsatellite (short tandem repeat) profiles of 7,121 individuals from various parts of the world residing or applying to live in the UK and Ireland . The six-population database is used in a forensic setting to ascertain distant relatedness or ancestry according to

92-731: Is available at the end of this article. F ST values depend strongly on the choice of populations. Closely related ethnic groups, such as the Danes vs. the Dutch , or the Portuguese vs. the Spaniards show values significantly below 1%, indistinguishable from panmixia. Within Europe, the most divergent ethnic groups have been found to have values of the order of 7% ( Sámi vs. Sardinians ). Larger values are found if highly divergent homogenous groups are compared:

115-668: Is closer genetically to an unrelated individual of their ancestral population than to their mixed half-sibling. In their study The History and Geography of Human Genes (1994) , Cavalli-Sforza, Menozzi and Piazza provide some of the most detailed and comprehensive estimates of genetic distances between human populations, within and across continents. Their initial database contains 76,676 gene frequencies (using 120 blood polymorphisms), corresponding to 6,633 samples in different locations. By culling and pooling such samples, they restrict their analysis to 491 populations. They focus on aboriginal populations that were at their present location at

138-423: Is not a consequence of the average diversity within subpopulations, where diversity is measured by the probability that two randomly selected alleles are different, namely 2 p ( 1 − p ) {\displaystyle 2p(1-p)} . If the allele frequency in the i {\displaystyle i} th population is p i {\displaystyle p_{i}} and

161-739: Is recorded on a number of police databases. This is as required under section 95 of the Criminal Justice Act 1991 , which states that: (1) The Secretary of State shall in each year publish such information as he considers expedient for the purpose of— The codes are also known as PNC or Phoenix Codes , or the 6+1 system . Other individuals involved in security and law enforcement, such as environmental enforcement officers, street wardens , guardians ( Cheltenham ), city guardians (Broad Street, Westminster City Council ), police community support officers , revenue protection inspectors , security guards and door supervisors , also use IC codes on

184-429: Is the probability that two individuals from the total population are identical by descent. Using this definition, F ST can be interpreted as measuring how much closer two individuals from the same subpopulation are, compared to the total population. If the mutation rate is small, this interpretation can be made more explicit by linking the probability of identity by descent to coalescent times : Let T 0 and T denote

207-463: The British police in radio communications and crime recording systems to describe the apparent ethnicity of a suspect or victim. Originating in the late 1970s, the codes are based on a police officer's visual assessment of an individual's ethnicity, as opposed to that individual's self-definition. In most circumstances where an individual's ethnicity is recorded after spoken contact with police (such as

230-402: The average number of pairwise differences between two individuals sampled from different sub-populations ( π Between {\displaystyle \pi _{\text{Between}}} ) or from the same sub-population ( π Within {\displaystyle \pi _{\text{Within}}} ). The average pairwise difference within a population can be calculated as

253-403: The fixation index (FST) measure of genetic distance. Fixation index This comparison of genetic variability within and between populations is frequently used in applied population genetics . The values range from 0 to 1. A zero value implies complete panmixia ; that is, that the two populations are interbreeding freely. A value of one implies that all genetic variation is explained by

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276-495: The Sardinians. The mean genetic distance among the 861 available pairings of the 42 selected populations was found to be 0.1338. . The following table shows Fst calculated by Cavalli-Sforza (1994) for some populations: A 2012 study based on International HapMap Project data estimated F ST between the three major "continental" populations of Europeans (combined from Utah residents of Northern and Western European ancestry from

299-723: The average time to coalescence for individuals from the same subpopulation and the total population, respectively. Then, This formulation has the advantage that the expected time to coalescence can easily be estimated from genetic data, which led to the development of various estimators for F ST . In practice, none of the quantities used for the definitions can be easily measured. As a consequence, various estimators have been proposed. A particularly simple estimator applicable to DNA sequence data is: where π Between {\displaystyle \pi _{\text{Between}}} and π Within {\displaystyle \pi _{\text{Within}}} represent

322-428: The data analyzed are highly polymorphic. In this case, the probability of identity by descent is very low and F ST can have an arbitrarily low upper bound, which might lead to misinterpretation of the data. Also, strictly speaking F ST is not a distance in the mathematical sense, as it does not satisfy the triangle inequality . Two of the most commonly used definitions for F ST at a given locus are based on 1)

345-409: The end of the 15th century when the great European migrations began. When studying genetic difference at the world level, the number is reduced to 42 representative populations, aggregating subpopulations characterized by a high level of genetic similarity. For these 42 populations, Cavalli-Sforza and coauthors report bilateral distances computed from 120 alleles. Among this set of 42 world populations,

368-691: The greatest genetic distance observed is between Mbuti Pygmies and Papua New Guineans, where the Fst distance is 0.4573, while the smallest genetic distance (0.0021) is between the Danish and the English. When considering more disaggregated data for 26 European populations, the smallest genetic distance (0.0009) is between the Dutch and the Danes, and the largest (0.0667) is between the Lapps and

391-401: The highest such value found was at close to 46%, between Mbuti and Papuans . A genetic distance of 0.125 implies that kinship between unrelated individuals of the same ancestry relative to the world population is equivalent to kinship between half siblings in a randomly mating population. This also implies that if a human from a given ancestral population has a mixed half-sibling, that human

414-446: The population structure, and that the two populations do not share any genetic diversity. For idealized models such as Wright's finite island model , F ST can be used to estimate migration rates. Under that model, the migration rate is where m is the migration rate per generation, and μ {\displaystyle \mu } is the mutation rate per generation. The interpretation of F ST can be difficult when

437-443: The relative size of the i {\displaystyle i} th population is c i {\displaystyle c_{i}} , then Alternatively, where f 0 {\displaystyle f_{0}} is the probability of identity by descent of two individuals given that the two individuals are in the same subpopulation, and f ¯ {\displaystyle {\bar {f}}}

460-560: The same title formed as a letter–number combination. If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=IC2&oldid=1050071444 " Category : Letter–number combination disambiguation pages Hidden categories: Short description is different from Wikidata All article disambiguation pages All disambiguation pages IC codes IC codes ( identity code ) or 6+1 codes are codes used by

483-416: The sizes of the subpopulations, and σ T 2 {\displaystyle \sigma _{T}^{2}} is the variance of the allelic state in the total population, F ST is defined as Wright's definition illustrates that F ST measures the amount of genetic variance that can be explained by population structure. This can also be thought of as the fraction of total diversity that

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506-408: The sum of the pairwise differences divided by the number of pairs. However, this estimator is biased when sample sizes are small or if they vary between populations. Therefore, more elaborate methods are used to compute F ST in practice. Two of the most widely used procedures are the estimator by Weir & Cockerham (1984), or performing an Analysis of molecular variance . A list of implementations

529-436: The variance of allele frequencies among populations, and on 2) the probability of identity by descent . If p ¯ {\displaystyle {\bar {p}}} is the average frequency of an allele in the total population, σ S 2 {\displaystyle \sigma _{S}^{2}} is the variance in the frequency of the allele among different subpopulations, weighted by

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