What is DNA and its role in genealogical research?
No matter how many birth, death and marriage documents you acquire doing genealogical research, DNA testing seems to have become a standard practice when searching for surname and male/female line inheritance.
Be aware though, that once in awhile, a guest speaker at a genealogical meeting will try to impress the audience with words like haplogroup and nucleotide polymorphism — terms that promote confusion for anyone not a molecular biologist.
Actually, DNA is a simple molecule with only four components called bases. These components produce patterns containing a linear sequence of genes. Most cells in humans have 23 pairs of chromosomes which contain genes inherited from your parents and re-combine parts of themselves to produce someone who is half father and half mother. The re-combination makes each child slightly different from its siblings, except with identical twins.
We all have individual genetic bar codes that stretch way back in time. The closer the relationship between two people, the more similar their DNA will be, and therefore it is possible to identify closely-related people who live far apart such as in Great Britain, America or Australia.
Females have XX chromosomes with one X contributed by each parent. Males have YX chromosomes. The Y comes only from the father, and his father, and his father, and his father...you get the idea. It is this Y component that allows us to follow our paternal line back several generations.
There are short, repeated segments of DNA at various places between the actual genes on the Y-chromosome. These short repeats are called markers and it is the number of these markers and various spaces between that can be read like a barcode. Typically a Y-DNA test will analyze a number of these repeats at 37,67,or 111 markers. It is the similarity or differences in this pattern that will show an estimate of relatedness. The more markers tested, the more refined the answer.
An autosomal test refers to the other 22 pairs of chromosomes also inherited from your parents, but the re-combination means there is no straight line relationship back to all ancestors; but this test does show relatedness across all lines between individuals back about seven generations — fifth cousins and closer within about 200 years and found in typical family trees.
A mitochrondrial test refers to cells uniquely inherited from the mother which contain their own DNA. You can use this test to trace a line from a man or woman through the mother, her mother, her grandmother, and so on although it doesn’t follow a single surname but can offer a link to a known maternal line.
So you see, it’s best to test with a company that offers both types of tests and has a large database such as www.ftdna.com.. Family tree has about 12 million bases in the male-specific region of the Y-Chromosome.
Hint: If you have a Scots background, remember an area can be made of many groups, e.g. Picts, Britons, Gaels, Norse, Irish, and Anglo-Danes. And, don’t forget, Celtic is a culture, not an ethnicity.
Carole Etchells Cross is a member of the Coshocton County Genealogy Society, which meets from 7:30 to 9 p.m. the third Tuesday of every month in the basement of the Coshocton Public Library. For more information, visit www.coshoctongenealogy.org.