Explaining the DNA Spreadsheet
Learning about DNA is done a step at a time…it’s not too terribly complicated...but it sure looks complicated.
The web site at http://blairgenealogy.com/dna/dna101.html is considered the basics but it tends to create as many questions as it answers. The spreadsheet is divided into 6 groups. Each group contains the related parties. Each group is unrelated to the other groups. Each test result is a set of 25 numbers... the value of the number is immaterial. The test scores are only useful when comparing them to someone else's test score to see how similar are the results.
The rule of thumb is that on a 25 marker test, those who miss by MORE than 2 markers are most probably not related…3 mismatches may have some small (5-10%) chance of being related. With enough people taking the test, the laws of probability state that some will have 3 mismatches and are in fact related.
Geneticists talk in terms of probabilities. There is always some small probability of error or that people are related who don't appear to be related...it can never be stated with 100% probability that two people aren't related...the probability however can get very small. Geneticists are starting to do complicated analysis to measure the "genetic distance" between two people...so it is entirely possible to have more that 3 or more mismatches but with a mathematical adjustment from a complicated formula still be related.
To confuse the issue not all markers mutate at the same rate. Fast mutating markers are considered "hot spots" and are listed on the spreadsheet with black column headings, and a pink background. "Hotspots" are not as relevant as other markers for determining if people are related. In Group Two is a Joseph W. A. Childress, for example, who misses by 4 markers from the other members of Group Two...but all the mismatches are at fast mutating "hot spots". The President of FamilyTree DNA feels that one should rely on the more stable markers to confirm a relationship and use the fast mutating "hot spots" only to separate lineages within a group. So, as an example, Joseph W. A. Childress with 4 mismatching "hot spots" is judged primarily on his stable makers and is judged to be a Group Two Haplotype (DNA pattern).
The University of Arizona is studying the issue of hot spots and the entire field of interpreting DNA tests is still evolving.
When you get your test score, just compare your 25 numbers to others who have taken the test to see if you are a close match to anyone.
Gary Childress is the DNA Project director for Childers-Childress Family Association and if you have any question or wish to take part in the project please contact Gary at his Email Address London2005@charter.net
Click here to view the current DNA Project Results Chart
