A genealogical DNA test is a DNA-based test which looks at specific locations of a person's genome, in order to find or verify ancestral genealogical relationships or (with lower reliability) to estimate the ethnic mixture of an individual. Since different testing companies use different ethnic reference groups and different matching algorithms, ethnicity estimates for an individual will vary between tests, sometimes dramatically. 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: (1) autosomal, (2) mitochondrial (mtDNA), and (3) Y-DNA. Autosomal tests may result in a large amount of DNA matches (other test persons that the individual may be related to), along mixed male and female lines, each match with an estimated distance in the family tree. However, due to the random nature of which and how much DNA is inherited by each tested person from their common ancestors, precise conclusions can only be made for close relations. Traditional genealogical research, and the sharing of family trees, is typically required for interpretation of the results. Autosomal tests are also used in estimating ethnic mix. MtDNA and Y-DNA tests are much more objective. However, they give considerably fewer DNA matches, if any, since they are limited to relationships along a strict female line and a strict male line respectively. MtDNA and Y-DNA tests are utilized to identify archeological cultures and migration paths of a person's ancestors along a strict mother's line or a strict father's line. Based on MtDNA and Y-DNA, a person's haplogroup(s) can be identified. Only men can take Y-DNA tests, since women lack a Y chromosome. The first company to provide direct-to-consumer genetic DNA testing was the now defunct GeneTree. However, it did not offer multi-generational genealogy tests. In fall 2001, GeneTree sold its assets to Salt Lake City-based Sorenson Molecular Genealogy Foundation (SMGF) which originated in 1999.While in operation, SMGF provided free Y-Chromosome and mitochondrial DNA tests to thousands.Later, GeneTree returned to genetic testing for genealogy in conjunction with the Sorenson parent company and eventually was part of the assets acquired in the Ancestry.com buyout of SMGF in 2012. In 2000, Family Tree DNA, founded by Bennett Greenspan and Max Blankfeld, was the first company dedicated to direct-to-consumer testing for genealogy research. They initially offered eleven marker Y-Chromosome STR tests and HVR1 mitochondrial DNA tests. They originally tested in partnership with the University of Arizona. In 2007, 23andMe was the first company to offer a saliva-based direct-to-consumer genetic testing. It was also the first to implement using autosomal DNA for ancestry testing, which all other major companies now use. MyHeritage launched its genetic testing service in 2016, allowing users to use cheek swabs to collect samples. In 2019, new analysis tools were presented: autoclusters (grouping all matches visually into clusters) and family tree theories (suggesting conceivable relations between DNA matches by combining several Myheritage trees as well as the Geni global family tree).