dna.reinyday.com - Genealogical DNA Testing

 

  About Genealogical DNA Testing


Maternal Ancestry. A person's maternal ancestry can be traced by their mitochondrial DNA, or mtDNA for short. Both men and women possess mtDNA, but only women pass it on to their children. So anyone can trace their mother's mother's mother's mother's (etc.) ancestry.


Paternal Ancestry. A man's paternal ancestry can be traced by the DNA on their Y-Chromosome, or Y-DNA for short. Only men have a Y-Chromosome, which they inherited from their fathers and will pass on to their sons. So a man can trace his father's father's father's father's (etc.) ancestry. Since Y-chromosomes are passed from biological father to son and surnames are traditionally passed from father to son, tracing families with a Y-DNA test is the most common form of genealogical DNA testing.


Understanding DNA. DNA (deoxyribonucleic acid) is the chemical inside the nucleus of all cells that carries the genetic instructions for making living organisms. Human DNA comes in 23 pairs of chromosomes (46 total). DNA is made up of 4 nucleotides: G (guanine), C (cytosine), A (adenine), T (thymine), which are easy to remember as G-CAT. The particular order of nucleotides is called the DNA sequence, and a sequence specifies the exact genetic instructions required to create a particular trait in an organism.


What is Tested With Y-DNA. When testing the Y-Chromosome (found only in males), the lab does not look at DNA which codes specific genes. The test instead looks at "junk" DNA, where certain segments of nucleotides are repeated over and over, called STRs (Short Tandem Repeats). These segments are designated by numbers that begin with "DYS#" (DNA Y-chromosome Segment Number). When your DNA is tested, the lab will count the number of repeats at certain locations on your DNA. The results of your test will tell you the number of repeats at those locations. For example, at DYS#454, you are likely to have 11 repeats. The Y-Chromosome is the only chromosome inside the nucleus that gets passed on without alteration; all other chromosomes withing the nucleus have their genes "reshuffled" during the process of sex cell production. DNA Heritage has authored a fantastic tutorial about how to use DNA for genealogy.


What is Tested With mtDNA. An mtDNA test analyzes DNA found in the mitochondria (an organelle inside most cells), instead of the DNA in the nucleus of a cell, meaning not inside the 23 pairs of chromosomes. About 20 years ago, the mtDNA of a European woman in Cambridge was sequenced and this is known as the Cambridge Reference Sequence (CRS). All results today are compared with the CRS. The parts of the mtDNA that are sequenced are sections called HVS1 (hypervariable sequence 1) and HVS2 (hypervariable sequence 2), because these regions have the most variation. People also use the term HVR, which stands for hypervariable region. Specifically, HVR1 generally tests sites 16024-16324 and HVR2 generally tests sites 63-322. An mtDNA test will tell you your HVR1 Haplogroup and HVR mutations. These "mutations" or "transitions" are derivations from the CRS.


About the Test. A genealogical DNA test is conducted by taking a painless cheek scraping in the comfort and privacy of your own home. This test will determine a relationship with another person with either a 99.9% probability of YES or a 100% certainly that NO near term relationship existed.


MRCA. If there is a match, you will be told approximately how many generations back your most recent common ancestor (MRCA) existed. For the 37-marker Y-DNA test [source], the probabilities for an exact match are as follows:

  • 50% probability that the MRCA was less than 5 generations ago
  • 90% probability that the MRCA was no more than 16 generations ago
  • 95% probability that the MRCA was no more than 21 generations ago

"For a 12-marker test, the total range of generations for relatedness is 76.9, which is almost 2000 years, and well before the adoption of surnames." [source] This is why testing at least 37 markers is recommended. Using an MRCA Calculator can help you easily see the proability of how closely related you are to someone else.

For the mtDNA "Maternal Match" test and the mtDNAPlus "high resolution Maternal Match" test, the probabilities for an exact match are as follows:

  • mtDNA: 50% probability that the MRCA was no more than 52 generations ago (about 1300 years)
  • mtDNAPlus: 50% probability that the MRCA was no more than 28 generations ago (about 700 years)


Ancient Ancestry. Obviously, all humans are related. Our common ancestors are believed to have existed more than 200,000 years ago. Homo sapiens sapiens first appeared about 120,000 years ago in Africa and bordering areas of Southwest Asia. It was not until 50,000 years ago that they began to appear in Europe and East Asia. There are two leading contradictory theories that attempt to explain the evolution of Homo sapiens sapiens. If you are interested in learning more about our ancient ancestry, here is a great page on the evolution of early humans.


Recent Ancestry. Genealogical DNA tests allow you to identify your recent and far distant ethnic and geographic origins on your direct male line. In addition, there are specific genealogical DNA tests for:


Additional Information. To learn more, please select from one of the following links:

 

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