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Author Topic: Help me understand maternal DNA  (Read 1476 times)
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« on: April 04, 2007, 12:58:22 PM »

First of all, I am very ignorant of DNA and what it can really prove so please bear with me through my questions.

My maternal grandmother and her sister reportedly gave birth one day apart in the early 1920s.  The child my maternal grandmother reportedly had was not raised by her but rather by her mother (my great grandmother).  Many of the family believe this child actually belonged to my grandmother's sister whom we suspect had twins and fostered one off as my grandmother's.  Both these children are now dead so direct DNA is not possible. 

Is it possible to test male grandchildren (one known to be her grandson and the other suspected of being her sister's) of my grandmother and determine maternity?

I apologize in advance for asking such primary questions but the mystery had followed our family for over 80 years.  My grandmother raised the son she had prior to the questionable birth and the daughter she had the following year. 

The cost of testing is not part of this equation--just whether or not we could obtain a reasonable answer.

Thank you for any insight and direction.
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« Reply #1 on: April 19, 2007, 01:48:25 AM »

There are several different ways you could go at this and all of them have a very slim chance of resolving this family mystery.

First of all, Y-DNA (surname DNA) testing would not be relevant for you, since woman do not have the Y-chromosome.  This particular chromosome is handed down from father to son, so it can be used to help verify paper trails of paternal (father's father's father) ancestry.  Only males can be tested, but females can use this type of testing as well if they can use the DNA of certain male relatives.

There is another test that would be relevant for you, called Mitochondrial DNA testing (mtDNA).  Mitochondrial DNA is passed down from mother to child, so it can be used to trace maternal ancestry (mother's mother's mother).  Normally, mtDNA would be perfect for resolving something like this, but since everybody in your mystery is so closely related, you probably won't be able to get enough testing resolution to find out.

If you want to use mtDNA, you need to take a test, and you also need to find a child of the other woman to get tested to compare your results to.  Both tests would need to be of the highest resolution to increase your chances of success.  If the two tests DID match, you would be unable to resolve the mystery (95+ percent chance).  If the two tests did NOT match entirely, you would have a 1/3 chance of proving your theory.  Basically, you would just keep testing relatives (assuming enough are available) until you could track down in which generation the mutation occurred.  Since each test costs $495, this would be an expensive process, with only a slim chance of success.  However, even in the event of failure, you would still learn a great deal about your "deep" ancestry (where your ancestors lived thousands of years ago) and the test results would be useful for other genealogical research.

Order the Full Sequence test for $495 by clicking here

You could also look into autosomal DNA tests.  Basically, these are a form of paternity testing (or maternity testing in this case) that tests all the chromosomes, not just the Y or mtDNA.  Since autosomal DNA tests are rarely used in genealogy,  I know little about it...  A representative of one of the companies that offers this type of testing might be able to tell you more.  These types of tests are not normally used to test ancestry so many generations back, so I doubtful that they would be of much use to you.

I'm sorry that I'm not able to provide a clearer or concise answer, but your question deals with some pretty tricky issues that are difficult to explain.  I hope I gave you enough information to be useful.  If you have other questions or wish to discuss this further, feel free to respond.
« Last Edit: April 19, 2007, 01:55:01 AM by Biscuits » Logged
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« Reply #2 on: April 19, 2007, 04:44:44 PM »

Thank you so much for your patience and reply.  It rather appears this mystery will never be solved.  We had hoped since there were 2 grandsons (possibly) that we could determine if they had the same grandmother, but doesn't look as though that is the case.  I will look into the other method and see what we might be able to ascertain from it.

Again, thanks.
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