What do you think a DNA test will tell you?
For one to several hundred dollars, you can have a DNA test done. Before you order that test, ask one simple question: what will you do with the results? Even more pertinent may be: what will the company do with the results?
The New York Times on Sunday presented the story of Georgia Kinney Bopp--a genealogist with a mission. Should you happen to run into her, keep your mouth closed--literally. Ms. Bopp travels with a DNA kit and can be very persuasive. Ms. Bopp apparently cornered a second cousin in Reno, Nevada, pulled out a DNA kit, and convinced him to give her a sample.
To me, the interesting part of the story was the description of how limited the information is that Ms. Bopp gets when she gets results from a DNA test. According to the article,
DNA tests can deliver surprises. In some families, someone may discover, for example, that he or she lacks a DNA connection to their supposed blood relatives.
What would you do if you learned from a test that your mother was not your mother, or your grandfather was not your father's father? It happens. Is it accurate?
One DNA test will not be enough for much family history testing--even for a paternity test you need samples from both the supposed father and the child. So, if you're searching for your ancestors, prepare to pay for more than one test.
The article goes on to state:
The DNA tests have limitatiions, showing only small slices of genetic history. Here is why: a popular test, the Y-DNA, analyzes the chromosome that is passed virtually unchanged for generations from father to son. . . .Another test looks at mitochondrial DNA, a form that is passed from a mother to all her children. Both men and women can take the test.
The Y chromosome test tells you about only one male ancester in a generation, and the mitochondrial test tells you about only one female ancestor. . . .It doesn't take into account the fact that if you go back just 10 generations (300 years), you have 1,024 ancestors in that generation. Just seeing one ancestor, means you're looking at a very small slice.
Now, what does the company do with your DNA and/or the results of your test? If the results are fully anonymous, how do they send you the results? Will they add your DNA results to their database so others can check their DNA against yours? Did you hear about the adolescent who found his "anonymous" sperm donor through DNA database information on the Internet?
Have you ever wondered: How many kinds of DNA tests are there? Will you be able to understand the test results when you get them? What does 99% exclusion, 75% inclusion mean? If you "relate" to a tribe now living in Africa, does that mean your ancestors came from Africa? If you're black, but your DNA is 79% European and 21% Asian, are you still black?
None of these questions address the more dangerous side of DNA testing--the medical side. If you have a test for a "breast cancer gene" and the test result says you have a 50% chance of developing breast cancer, do you schedule a double mastectomy? Will your insurance pay for it? What will you tell your sister or your daughter about their chances of developing breast cancer?
Please don't blindly order a DNA test and send your personal genetic code off to some company you've only read about through an advertisement. Check into things first. It's too late once the results arrive.
Marie Godfrey, PhD
Paternity tests
The result of a paternity test is generally expressed in terms of inclusion/exclusion. For example, there is a 67% chance that the male tested is included among those who could be the father of this daughter. Or, there is a 95% chance that the male tested is excluded from possibly being the father. Or, the results are inconclusive.
The mother's DNA is not necessary, because half of the father's DNA will match half of the daughter's DNA and that may be enough for a "good" number. Check a site that offers paternity testing (you can google that) and look at their information on what DNA is needed and how the results are reported. The best bet is a site licensed in New York State or California. Generally, it matters whether the test is done to "include" someone or "exclude someone".
I'll check this out for you and respond to your comment again as soon as I find out more. Just arrived home after 12 hours travel by car, and am tired.
Paternity testing--is mother needed?
Here's what happens in the calculations of a paternity test done by one of the companies. Note that 19 possible patterns can be discerned if the mother participates in the testing, only 5 if the mother does not participate.
Paternity Calculations
The PI stands for Paternity Index and is independently calculated for each system analyzed. There are 19 possible patterns for each system analyzed that supports paternity...the first 14 patterns are possible when the mother of the child participates. The bottom 5 patterns are used for motherless calculations.
The single letter designation indicates that the individual is homozygous (has two copies of the same marker) in the system. For line "1" the Trio might look like (14,14) (14,14) (14,14)--the child would have inherited one 14 from their mother and one 14 from the father.
The double letter designation indicates that the individual is heterozygous in that system. Using line 3 for an example the markers could be (14,14) (14,15) (14,15)--the child has inherited the 14 from the mother and the 15 from the father. Each subsequent pattern can be interpreted in the same manner.
The pattern determines the formula to be used in each system. The lower case letter in the formula indicates the frequency of the marker observed in the pattern. The frequency of each marker (allele) is derived from applicable population database.
To best demonstrate how this works a table is constructed. The first column indicates the DNA system analyzed and the subsequent columns list the alleles for the mother, Child, and Father. For this example when a zero is indicated in a column it denotes a homozygous system.
Using the same table, patterns are assigned (noted in the yellow rows).
Once the patterns are recognized the proper formula can be applied. The frequency of the allele designated by the lower case letter is accessed from the applicable population database. The system designated as FGA in this example lists the frequency of the allele designated 20 as .1625.
That frequency is used in the formula dictated by the pattern and the result indicates the PI for that system.
That process is repeated for each subsequent system:
The individual PI's are multiplied together to calculate a Combined Paternity Index.
The Combined Paternity Index is the strength of the evidence supporting the hypothesis that the tested man is the biological father as compared to an untested, unrelated man.
The above example produces a CPI of 3,231.
I am not recommending this company, but showing what their reports and results are like.
Their report to you would look lie this:
How do I read the report?Each section of the standard paternity report is described in detail and can be accessed by selecting sections that require clarification on the example below.
Paternity testing
Can paternity be established by just drawing the blood of the husband and his daughter with out the mothers blood? A friend of mine has told me that he did this behind my back and it was a "secret" , we where going thru a divorce and no paternity test was requested thur the courts, there has never be a doubt , he is the only man I was with, however he is bizzare and admits to telling my friend he was going to have that done. I am just wondering if it can be done without my blood?
Curious mother