More and more, it seems that we see headlines which scream "Buyer Beware!" The latest one is in the New York Times today. That one is headlined "Buyer Beware of Home DNA Tests". A reader may think ... hmmm ... my yDNA or mtDNA test is a "home" dna test - so I should beware. Actually, I think you should always seek to learn more - as the best consumer is the aware consumer. However - the article is addressing a completely different type of test - tests which look at medical conditions.
yDNA and mtDNA are NOT the focus of this New York Times article. You should be informed - but not concerned - if you are using yDNA and mtDNA for genealogcal purposes.
For genealogy, we use yDNA and mtDNA tests, which can correctly be called "Genetic Genealogy". However, they are completely different from the tests which look at medical conditions - tests which can be called Genetic Tests.
yDNA and mtDNA tests are looking at a very specific part of your dna profile and are intended for genealogical purposes. They are not intended to evaluate medical conditions or the tendency to have a medical condition. (see note below)
yDNA uses information from the y-chromosome (the chromosome that makes a man a man) in surname projects to determine which men share a recent common paternal ancestor. (only men have yDNA - which they receive from their father)
mtDNA is in the mitochondria of each of us - the material that carries our genes. mtDNA is inherited by each person from their mother, so anyone can be tested for mtDNA, but only women can pass it on to their children. mtDNA sometimes can be helpful in a genealogical search.
Both yDNA and mtDNA are useful in looking at specific portions of our deep ancestry. I use the word "specific" because each is focused on a very specific portion of our ancestry. yDNA can be used to explore a man's ancient paternal ancestry (his father's father's ... father's paternal line) while mtDNA can be used to explore a person's ancient maternal ancestry (mother's mother's ... mother's maternal ancestry) The family of man and the family of woman are classified by scientists into "Haplogroups" which can be correlated to ancient migration patterns. In recent years, the research (often by genealogists as much as by scientists) is working on "Deep Clade" testing - which refines the Haplogroup precision, moving it to less ancient times. (We hope that someday the Deep Clades can be extended to modern times)
Autosomal tests look at dna which is inherited from both mother and father and is merged into a new array in an individual. This form of dna is primarily used for forensics and paternity. Researchers are exploring the possibility of using autosomal dna for genealogy.
So - you should be aware of what you are doing - and of what information you will get with a dna test. You should also be aware of what you can expect from the testing company. If you are in doubt - you should do your own research - or ask.
I have worked with yDNA for surname relatedness for more than 8 years and I have worked with FamilyTree DNA for more than 5 years. Family Tree DNA is an ethical company which works very hard to provide solid customer service. yDNA and mtDNA tests have been useful to me for genealogical and ancient ancestral purposes.
yDNA and mtDNA tests should not be included in discussions about genetic testing - particularly discussions where Doctors would be required to authorize and interpret the results. Quite frankly, we often have to explain our testing to Doctors - just like we have to explain it to the "layman".
Note: there are a few rare cases where a yDNA or mtDNA test can provide specific medical information. While I have not experienced one of these, I do know of people who have. If this is a concern to you, I would suggest that you maintain a confidentiality of your test identity until you see your own results and find if you are one of the very small minority with medical information. Then, if you are like the vast majority of us - you'll be unconcerned when you release your results to the project.