Y-DNA testing

A genealogical DNA test is a DNA-based test which looks at specific locations of a person's genome in order to determine ancestral ethnicity and genealogical relationships. Results give information about ethnic groups the test subject may be descended from and about other individuals that they may be related to.

Three principal types of genealogical DNA tests are available, with each looking at a different part of the genome and useful for different types of genealogical research: Autosomal, , and Y. In general, genealogical DNA tests do not give information about medical conditions or diseases.

Taking a genealogical DNA test requires the submission of a DNA sample. The most common way to collect a DNA sample, which can be done by either visiting a DNA test clinic or by ordering a home test through an independent DNA test supplier, is by a cheek-scraping (also known as a buccal swab). Other methods include spit-cups, mouthwash, and chewing gum. After collection, the sample is mailed to a testing lab.

Some laboratories, such as FamilyTreeDNA, offer to store DNA samples for ease of future testing.

There are three major types of genealogical DNA tests: Autosomal and X-DNA, Y-DNA and mtDNA. Autosomal tests look at Chromosomes 1-22 and X. The autosomes (chromosomes 1-22) are inherited from both parents and all recent ancestors.The X-chromosome follows a special inheritance pattern. Ethnicity estimates are often included with this sort of testing. Y-DNA looks at the Y-Chromosome, which is inherited father to son, and so can only be taken by males to explore their direct paternal line. mtDNA looks at the mitochondria, which is inherited from mother to child and so can be used to explore one's direct maternal line. Y-DNA and mtDNA cannot be used for ethnicity estimates, but can be used to find one's haplogroup, which is often associated with a particular ethnic group or region.

Autosomal DNA is the 22 pairs of chromosomes that do not contribute to sex. These are inherited exactly equally from both parents and roughly equally from grandparents to about 3x great-grand parents. Inheritance is more random and unequal from more distant ancestors. Generally, a genealogical DNA test might test about 700,000 SNPs (single-nucleotide polymorphisms). Like mtDNA and Y-DNA SNPs, autosomal SNPs are changes at a single point in genetic code. Autosomal DNA recombines each generation. Therefore, the number of markers shared with a specific ancestor decreases by about half each generation.

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