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Excerpts from Wikipedia.org Y Chromosome TestingA man's paternal ancestry can be traced using the DNA on his Y chromosome (Y-DNA) through Y-STR Testing. This is useful because the Y chromosome, like many European surnames, passes from father to son, and can be used to help study surnames. Women who wish to determine their paternal ancestry can ask their father, brother, paternal uncle, paternal grandfather, or a cousin who shares the same paternal lineage to take a test for them (i.e. any male family member who has the same surname as her father). Y-DNA tests generally examine 10-67 STR markers on the Y chromosome but over 100 markers are available. STR test results provide the personal haplotype. SNP results indicate the haplogroup. Mitochondrial DNA TestingA person's maternal ancestry can be traced using his or her Mitochondrial DNA (mtDNA). The DNA in the human mitochondria is passed down by the mother unchanged. One exception, which was linked to infertility, has been shown. Additionally, some people cite paternal mtDNA transmission as invalidating mtDNA testing, but this is not considered problematic in scholarly population genetics studies or genetic genealogy. mtDNA by current conventions is divided into three regions. They are the coding region and two Hyper Variable Regions (HVR1 and HVR2). All test results are compared to the mtDNA of a European in Haplogroup H2a2. This sample is known as the Cambridge Reference Sequence (CRS). A list of single nucleotide polymorphisms (SNPs) is returned. Any "mutations" or "transitions" that are found are simply differences from the CRS. The test results are compared to another person's results to determine the time frame in which the two people shared a most recent common ancestor (MRCA). The two most common mtDNA tests are a sequence of HVR1 and a sequence of both HVR1 and HVR2. Some people are now choosing to have a full sequence performed. This is still somewhat controversial as it may reveal medical information.
Ethnic TestsAutosomal tests that test the recombining chromosomes are available. These attempt to measure an individual's mixed ethnic heritage. The tests' validity and reliability have been called into question but they continue to be popular. Autosomal DNA testing purports to determine the "genetic percentage" of certain ethnicities in a person. These tests examine SNPs, which are locations on the DNA where one nucleotide has "mutated" or "switched" to a different nucleotide. These tests are designed to tell what percentage Native American, European, East Asian, and African a person is. These tests are controversial—their validity has not been independently confirmed — and the results are often disputed. One company (Ancestry by DNA) describes these four ethnic groups: Native American, European, East Asian, African. Based on customer feedback, the company in June 2007 introduced a new version of its EURO DNA test with a more limited range of countries that promises to have more meaningful clues to one's European ancestry. Both tests -- the four-part ethnicity estimate and EURO DNA test -- use a high number of so-called Ancestry Informative Markers whose genetic distance between populations reflects the populations' geographic distance from each other. The location and variation of these AIMs are proprietary to the company, which is publicly held, and have never been published. In 2006, another company (DNA Consulting) developed an autosomal DNA ancestry-tracing product that combined the traditional CODIS markers used by law enforcement officers and the judicial system with OmniPop, a population database developed by San Diego detective Brian Burritt. Customers received matches to their profile's frequency of occurrence in world populations as well as a breakout for European ancestry based on the European Network of Forensic Science Institutes, or ENFSI. As a public service, the company has supported the expansion of OmniPop, which currently encompasses over 300 populations, double that of its first release. The ENFSI calculator uses data from 24 European populations (5700 profiles). The two databases must be searched separately, however, because they are based on two different sets of markers. The company sells its product as the DNA Fingerprint Test. The 16 markers incorporated in its results are: D8S1179, D21S11, D7S820, CSFIPO, D3S1358, THO1, D13S317, D16S539, D2S1338, D19S433, VWA, TPOX, D18S51, D5S818, and FGA. The theory behind using a forensic profile for ancestry tracing is that the alleles' respective frequency of occurrence develops over generations with equal input of the two parents since for each location we take one value from our mother and one from our father. It thus serves as a window into a person's total ancestral composition. The configuration of scores reflects inherited changes from all previous generations, all ancestral lines, and can predict an individual's unique probable ethnic matches based on the profile's commonness or rarity in different populations. The only validation study so far is one by Donald N. Yates and Elizabeth C. Hirschman based on company files. However, neither Yates nor Hirschman are professional geneticists. As marker sets from more and more populations are included, it is expected that the accuracy of results should improve, leading to a more informative picture of one's ancestry. Along the same lines, yet another company (DNA Tribes) identifies the indigenous and diaspora populations in which an individual's autosomal STR profile is most common. This test examines autosomal STRs, which are locations on a chromosome where a pattern of two or more nucleotides is repeated and the repetitions are directly adjacent to each other. The populations in which the individual's profile is most common are identified and assigned a likelihood score. The individual's profile is assigned a likelihood of membership in each of twenty three world regions. This STR analysis measures the frequency of a person's DNA profile within major world regions. Unlike SNP admixture tests, this analysis is based on objectively identified world regions and does not depend on any system of presumed biogeographic classifications. However, as most STR analysis examines markers chosen for their high intra-group variation, the utility of these particular STR markers to access inter-group relationships may be greatly diminished.
Human Leukocyte AntigenThe human leukocyte antigen system (HLA) is the name of the major histocompatibility complex (MHC) in humans. This group of genes resides on chromosome 6, and encodes cell-surface antigen-presenting proteins and many other genes. The major HLA antigens are essential elements in immune function:
HLAs also have a role in:
Aside from the genes encoding the 6 major antigens, there are a large number of other genes, many involved in immune function located on the HLA complex. Diversity of HLA in human population is one aspect of disease defense, and, as a result, the chance of two unrelated individuals having identical HLA molecules on all loci is very low. A HLA Haplotype is a series of HLA "genes" (loci-alleles) by chromosome, one passed from the mother and father. Example: A*0101 : Cw*0701 : B*0801 : DRB1*0301 : DQA1*0501 : DQB1*0201 - which is called ' 'super B8' '. These haplotypes can be used to trace migrations in the human population because they are often much like a fingerprint of an event that has occurred in evolution. The Super-B8 haplotype is enriched in the Western Irish, declines along gradients away from that region and is only found in areas of the world where Western Europeans have migrated. The Super-B8 haplotype is associated with a number of diet associated autoimmune diseases (See HLA DR3-DQ2 and celiac disease). |
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