Types of dna test suitable for genealogy purposes
What's best for a genealogy test?
Genealogy and DNA testing
Who passes dna to whom?
Heritage dna testing.
Types of DNA test
There are several types of dna test. This is often a surprise to the novice, probably because the media tends to use the term 'dna test' rather freely and generically, so it's easy to make the assumption that there is just the one, definitive, test.
Brothers Tim & Brian seem proud to share the same Y-DNA
In fact there are many types of dna test. For the purposes of genealogy, however, where we can ignore those methods of testing designed for gathering criminal (forensic) evidence or the study of genetic (medical) conditions, there are currently just three.
The main features and results of these different 'genealogy tests' are examined briefly below.
This page is intended to provide an overview of current heritage dna testing options.
For a more in-depth look at each option, see the Related Pageslinks in the right-hand column.
The Y-dna test.
Y-Line or Y-dna testing is by far the most popular of the three types of dna test, for reasons that soon become obvious. The test tracks the Y-chromosone, which is passed down the generations from father to son.
Y-dna testing and genealogical surname studies are a perfect marriage
Woman don't have a Y-chromosone so they cannot take this test (although a woman who wants to explore her paternal genealogy can simply ask her father, brother, paternal uncle or his son to take a test).
What is special about the Y-chromosone is its continuity down the generations, along with the surname of the paternal line. And this is why Y-dna testing and genealogical surname studies are a perfect marriage.
When the dna is sampled by the testing lab, tiny chemical markers on the chromosone create a distinctive pattern. This pattern is known as a haplotype, and it distinguishes one male line from another.
If the haplotype is shared with another individual, it can indicate that the two have a common ancestor.
It does not, however, confirm which ancestor, nor the exact degree of the relationship.
The MtDNA test.
Mitochondrial dna is usually abbreviated to mtDNA but these types of dna test are often referred to as Deep Ancestry Tests.
These siblings all have their mother's mtDNA,
but only the girls can pass it to the next generation.
An mtDNA analysis is used to trace the maternal line because this type of dna is passed only from mother to child. (A man cannot pass on mtDNA to his children.)
mtDNA is passed intact, ie without any mixing, so if two people find an exact match, it indicates they share a common ancestor.
What cannot be determined, however, is whether that common ancestor was a recent one, or many many centuries and generations back.
For this reason, and the fact that women's names traditionally change with each generation (when they adopt their husband's family name), mtDNA testing isn't usually used to see if people are related to one another or to find common ancestors.
While it hasn't, therefore, been much used for genealogy purposes, recent scientific discoveries suggest this may be about to change.
In the meantime, these types of dna test are principally used to discover etnic origin.
The 'Ethnic Test' – Autosomal DNA Testing
These tests are relatively new, and come with a good mix of controversy attached. Some dismiss their genealogical value and reliability altogether.
Others think there is some considerabale research and development to be done before they can be taken too seriously.
Even so, they are becoming quite popular. Autosomal DNA is usally abbreviated to at-DNA.
For the simple fact that they don't much to do with genealogy research, I'm not going to go into much detail with them.
Because dna inherited from both parents is analysed, autosomal dna testing purports to uncover a person's total ancestral heritage, not just that from the maternal or paternal line, as is the case with the other main types of dna tests.
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