Post by Robin on Mar 30, 2014 1:09:14 GMT
DNA can be confusing and I don't pretend to understand everything involved but this should be a good beginner's guide to understanding the differences between the three types of tests available for genealogists: yDNA, mtDNA, and atDNA.
yDNA
yDNA will test strictly your paternal line (the y chromosome) and therefore can only be taken by men. If you are a woman, you may have a male relative like a brother, father, or male cousin who would be willing to do the test for you. The data from this test will be only from your father, your father's father, your father's father's father, etc - you will not get data from anyone else in your tree. So if you're looking for answers to questions like "Do I have Native American heritage?" this is not the test for you unless the suspected Native American heritage is from the paternal line. What this test will tell you is your paternal haplogroup, which will show you the origins and migrations of your paternal line over thousands of years and allow you to join DNA Surname Projects. There are different types of yDNA tests, with different pricing, depending on how many markers you want to test. The more markers tested, the better the results, so the more expensive the test will be.
mtDNA
mtDNA tests are like the maternal version of yDNA tests, the data results come from mitochondrial DNA which is passed from mother to child. Unlike yDNA, both men and women have mitochondrial DNA, which means both can use this test, but only women pass it on and therefore the data will show results from strictly the maternal line; your mother, your mother's mother, your mother's mother's mother, etc. Again, this is not useful for determining suspected ethnic heritages unless you believe it to be in the strictly maternal line but it will show the origins and migrations of your maternal line over thousands of years and tell you which "daughter of Eve" you are descended from or which mitochondrial haplogroup you belong to.
atDNA
atDNA or Autosomal DNA is different, it does not test merely one straight line of your tree, but the full spectrum. However, it can only provide results for the full spectrum that you inherited. atDNA inheritance is fairly random, so just because you have an Italian great grandparent doesn't mean you're exactly 25% Italian, you might be more like 40% or 15%. However, the more closely related that ancestor is to you, the more likely you inherited a larger percentage of atDNA from them and the longer ago that they lived, the less likely it is you inherited an atDNA from them at all. So unlike yDNA and mtDNA, this does not go back thousands of years, it's best for understanding your more recent heritage. What this means is that if you're trying to prove that your 7th great grandmother was, for example, Native America, this test might confirm it but it can't deny it. If your test results come back with what will likely be a small percentage of Native American DNA, it's confirmed, but if there's no trace of Native American DNA, that might just mean you didn't happen to inherit anything from that particular ancestor. It doesn't necessarily mean you never had a Native American ancestor.
It's also important to know that the ethnicity percentages from atDNA are approximate and most companies will give you a range rather than a hard and fast number.
Also important is understanding that DNA is not confined to political or national borders. The test results won't say "you're 30% Italian", they'll probably say something more like "30% Mediterranean" or "30% Italy/Greece", which will include other nearby areas too. It's your job, as a genealogist, to have some understanding of your heritage already so you know when they say something like "Mediterranean", it's probably your Italian heritage, or when they say "10% Scandinavian", you know it's your Norwegian ancestry.
The current standard pricing for atDNA tests is $99 USD.
More reading:
Hiring a DNA Testing Company - FamilySearch.org
Maternal Lineage Test - Ancestry.com
Paternal Lineage Test - Ancestry.com
Information about Paternal Lineage (Y-DNA) testing - Ancestry.com
Information about Maternal Lineage (mtDNA) testing - Ancestry.com
yDNA
yDNA will test strictly your paternal line (the y chromosome) and therefore can only be taken by men. If you are a woman, you may have a male relative like a brother, father, or male cousin who would be willing to do the test for you. The data from this test will be only from your father, your father's father, your father's father's father, etc - you will not get data from anyone else in your tree. So if you're looking for answers to questions like "Do I have Native American heritage?" this is not the test for you unless the suspected Native American heritage is from the paternal line. What this test will tell you is your paternal haplogroup, which will show you the origins and migrations of your paternal line over thousands of years and allow you to join DNA Surname Projects. There are different types of yDNA tests, with different pricing, depending on how many markers you want to test. The more markers tested, the better the results, so the more expensive the test will be.
mtDNA
mtDNA tests are like the maternal version of yDNA tests, the data results come from mitochondrial DNA which is passed from mother to child. Unlike yDNA, both men and women have mitochondrial DNA, which means both can use this test, but only women pass it on and therefore the data will show results from strictly the maternal line; your mother, your mother's mother, your mother's mother's mother, etc. Again, this is not useful for determining suspected ethnic heritages unless you believe it to be in the strictly maternal line but it will show the origins and migrations of your maternal line over thousands of years and tell you which "daughter of Eve" you are descended from or which mitochondrial haplogroup you belong to.
atDNA
atDNA or Autosomal DNA is different, it does not test merely one straight line of your tree, but the full spectrum. However, it can only provide results for the full spectrum that you inherited. atDNA inheritance is fairly random, so just because you have an Italian great grandparent doesn't mean you're exactly 25% Italian, you might be more like 40% or 15%. However, the more closely related that ancestor is to you, the more likely you inherited a larger percentage of atDNA from them and the longer ago that they lived, the less likely it is you inherited an atDNA from them at all. So unlike yDNA and mtDNA, this does not go back thousands of years, it's best for understanding your more recent heritage. What this means is that if you're trying to prove that your 7th great grandmother was, for example, Native America, this test might confirm it but it can't deny it. If your test results come back with what will likely be a small percentage of Native American DNA, it's confirmed, but if there's no trace of Native American DNA, that might just mean you didn't happen to inherit anything from that particular ancestor. It doesn't necessarily mean you never had a Native American ancestor.
It's also important to know that the ethnicity percentages from atDNA are approximate and most companies will give you a range rather than a hard and fast number.
Also important is understanding that DNA is not confined to political or national borders. The test results won't say "you're 30% Italian", they'll probably say something more like "30% Mediterranean" or "30% Italy/Greece", which will include other nearby areas too. It's your job, as a genealogist, to have some understanding of your heritage already so you know when they say something like "Mediterranean", it's probably your Italian heritage, or when they say "10% Scandinavian", you know it's your Norwegian ancestry.
The current standard pricing for atDNA tests is $99 USD.
More reading:
Hiring a DNA Testing Company - FamilySearch.org
Maternal Lineage Test - Ancestry.com
Paternal Lineage Test - Ancestry.com
Information about Paternal Lineage (Y-DNA) testing - Ancestry.com
Information about Maternal Lineage (mtDNA) testing - Ancestry.com