To read the article in full, hit here by Family Tree Editors
The ABCs of DNA and Genetic Genealogy
Genetic genealogy and DNA testing is a frontier is brimming with the potential for answers. By examining your genes, scientists can tell whether you share an ancestor with someone, about how long ago that common ancestor lived, and your ethnic origins.
Autosomal DNA (also called atDNA or admixture DNA)
Genetic material inherited equally from mother and father. It’s genealogically useful for ancestry back through about five to seven generations. Beyond that, you may not have inherited enough DNA from any one ancestor for that person to be represented in your autosomal DNA.
If you’re new to genetic genealogy, autosomal DNA testing is probably what you’ve heard about. Ninety-nine percent of your DNA is autosomal. Both male and female children inherit autosomal DNA equally but randomly from both parents. Thus, siblings on average have 50 percent overlapping DNA (except for identical twins, whose DNA is 100 percent the same). First cousins have on average 25 percent overlapping DNA.
Details about atDNA
Based on the amount of autosomal DNA you share with a match, test results can tell you approximately how far back your common ancestor lived and estimate your relationship. It’s up to you to determine who that ancestor might be, by studying your DNA match list, comparing your genealogy info with your matches’, and doing paper research.
Autosomal tests aren’t helpful farther back than five or six generations, though, because at that point you don’t have enough DNA from any one ancestor for it to be reflected on your test.
Autosomal tests also express your ancestry in terms of percentages from various ethnicities or geographic origins, such as Scandinavian, British, Eastern European, etc. This breakdown depends on what “reference populations” the testing company compares your results to, so you might get different results from different companies. It’s a developing but promising field: With more research, companies are improving ethnicity estimates and can even use results to predict ancestors’ migration paths.
Centimorgan (cM)
A measurement of the distance between genetic markers on the DNA based on the expected frequency of recombination with each generation. On average, one cM equals one million base pairs. In general, the more centimorgans you share with a genetic match, the closer your relationship (although individuals related through multiple ancestors also may share a high number of centimorgans).
More terms online
To get your free download you will have to go online and enter your email address.
