I have had DNA tests done through two laboratories: Family Tree DNA and 23andme.
Family Tree DNA is one of the oldest of the DNA labs, concentrating on DNA testing primarily for genealogy research. I had my Y-DNA test done thee several years ago, while researching potential connections with small group of Lewis descendants who turn out to have DNA results very similar to mine.
23andme is a health-realted DNA lab that has recently expanded their services to include DNA testing for genealogy research. The test from 23andme includes the Y-DNA test (for men only) along with mitochondrial and chromosomal tests, to give results that includes ancestors on both sides of the subject's DNA legacy. You can go to the 23andme web site and learn much more about this fascinating new form of genealogy research.
Y-DNA - The Y-DNA test records the Y chromosome to reveal my DNA legacy from my paternal line: my father, grandfather, great-grandfather... and so on. Y-DNA tests are characterized by specific markers that form patterns known as haplogroups. My haplogroup is R1b1b2a1a, a subgroup of R1b1b2, the most common haplogroup in western Europe. R1b1b2a1a1 is most commonly found on the fringes of the North Sea, and is know as the "North Atlantic Subgroup." It is about 17,000 years old, being found in Irish, Basque, British and French populations.
mtDNA - The mitochondrial DNA test records the DNA from mitochondria in the cells to reveal my DNA legacy from my maternal line: my mother, grandmother, great-grandmother... and son on. mtDNA results have haplogroups, just as do Y-DNA results. My mtDNA haplogroup is K1a4, a subgroup of haplogroup K, about 350,000 years old in the Near East, Europe, Central Asia and northern Africa.
My chromosomal DNA reveal that 98.7% of my DNA is from northern and eastern Europe, .8% is from the Middle East and .5 % is unassigned. This result reflects where my ancestors we living 500 or more years ago, before modern transportation allowed us to move rapidly about the globe.