DNA Testing Genealogy
A genealogical DNA test in done by taking a painless cheek-scraping, which is referred to as a buccal swab. These can be taken in the comfort of your own home and mailed to a genetic genealogy laboratory for testing. There are some laboratories that use mouth wash or chewing gum rather than cheek swabs.
Y chromosome (Y-DNA) testing and mitochondrial DNA (mtDNA) testing are the most popular ancestry tests. Other tests attempt to determine a person’s comprehensive genetic history and/or ethnic origins.
The paternal ancestry of a man can be traced using the DNA on his Y chromosome through Y-STR testing. This is useful because the Y chromosome passes from father to son, which can assist an individual in studying surnames. Women who wish to determine their paternal ancestry would need to ask a male relation, such as their father, brother, cousin, paternal uncle, or paternal grandfather, to take the test on their behalf.
Y-DNA testing involves looking at segments of DNA on the Y chromosome, which is found only in males. The segments which are examined are referred to as genetic markers and occur in what is considered “junk” DNA.
Y-DNA tests generally examine 10-67 STR markers on the Y chromosome, however, over 100 markers are in fact available. STR test results provide the personal haplotype. SNP results indicate the haplogroup.
A Y-DNA haplotype is the numbered results of a genealogical Y-DNA test. Each allele value has a distinctive frequency within a population.
Haplogroups are large groups of haplotypes that can be used to describe genetic populations and are often geographically oriented. Y-DNA haplogroups are determined by SNP tests. SNPs are locations on the DNA whereby one nucleotide has “mutated” or “switched” to a different nucleotide. This switch must occur in a minimum of 1% of the population in order to be considered a useful SNP. If it is less than 1% of the population, it is considered a personal SNP.
Autosomal tests are also available, which test the recombining chromosomes. These tests measure an individual’s mixed geographic heritage by identifying particular makers, which are called ancestry informative markers or AIM. These are associated with populations of specific geographical areas. The validity and reliability of the tests have been called into question; however, they do continue to be popular.
It is claimed that autosomal DNA testing determines the “genetic percentages” of a person’s ancestry from particular continents/regions, or list the countries and “tribes” of origin on an overall basis. Admixture tests arrive at percentages by examining SNPs, which are locations on the DNA where one nucleotide has “mutated” or “switched” to a different nucleotide.
The people of the United States have been interested in using genealogical DNA in order to help them to learn more about their ancestry. This is because of the history if immigration, slavery, and significant indigenous peoples.
Autosomal testing, Y-DNA, and mtDNA testing can all be conducted to establish Amerindian ancestry.
It may be established as to whether a person’s direct female line belongs to one of the canonical Native American DNA Haplogroups A, B, C, D, or X by undertaking a mitochondrial Haplogroup determination test. If a person’s DNA belonged to one of those groups, then the implication would be that he or she is, in whole or part, Native American.
Y-DNA and mtDNA testing may assist in determining with which peoples in present-day African country a person shares a direct line or part of his or her ancestry, but patterns of historic migration and historical events cloud the tracing of ancestral groups. One testing company by the name of ‘African Ancestry’ maintains an ‘African Lineage database’ of African lineages from 30 countries and over 160 ethnic groups. Approximately 30% of African American males have a European Y chromosome haplogroup. Approximately 58% of African Americans have the equivalent of one great-grandparent of European ancestry, and only 5% have the equivalent of one great-grandparent of Native American ancestry.
Almost three-quarters of African Americans taken in slavery came from regions of West Africa. The African-American movement to discover and identify with ancestral tribes has multiplied since DNA testing became available.
Genealogical DNA tests have become increasingly popular over recent times because it is simple to undertake the test in the comfort of your own home. Genealogical DNA tests allow for an individual to determine with 99.9% certainly whether they are related to another person within a particular time frame, or with 100% certainty that they are not related.
However, there is considered to be certain drawbacks when it comes to genealogical DNA testing. These drawbacks include cost and privacy issues. The most common complaint from DNA test customers is the failure of the company to make results understandable and significant to them. According to a survey taken, 1 in 6 Americans said that they were unaware of the ancestry-tracing capability of a home DNA test, and when probed, most knew little about the details, reliability, or differences between tests.
There can also be complications involved in the Y-DNA lineage from father to son including unusual mutations, secret adoptions, and false paternity. Maternal DNA is hard to correlate with surnames due to the fact that surnames are not generally passed on from women. Another drawback is that their present state of imperfection and large margin of error with significant blind spots, such as confusion of Mongolian ancestry with Native American.
Even though the results of genealogical DNA tests generally have no informative medical value and are not intended to determine genetic diseases or disorders, there has been a link established between a lack of DYS464 markers and infertility, and a link between mtDNA haplogroup H and protection from sepsis. There have been particular haplogroups linked to longevity.
It still remains somewhat controversial as to the testing of full mtDNA sequences. This is because it may reveal medical information. The field of linkage disequilibrium, unequal association of genetic disorders with a certain mitochondrial lineage, is in its infancy; however, those mitochondrial mutations that have been linked are searchable in the genome database Mitomap. The Genetic and Rare Disease Information Center is operated by the National Human Genome Research Institute, and this can assist consumers in identifying an appropriate screening test and help locate a nearby medical center that offers such.
There are some genealogy software programs that allow recording DNA marker test results, which allows for the tracking of both Y-chromosome and Mitochrondrial DNA tests and results for relatives. There are also DNA wall charts available.