I know there are tests which rely on mtDNA and Y-Chromosome and they require all-female and all-male lines.
I am interested in finding out if one branch of my family is related to another, just because the circumstances concerning my great-grandmother are fishy; my great-great-grandfather was told that he had a kid, so he went back to get my g-grandmother. But how did he know she was his? lol
So my great-grandmother passed on in 1985. She has one half sister still alive, but in the Philippines. Another half-sister died in 2006 but her descendants live in Montreal & Portland so it'd be easier to test them.
My question if it's possible to establish a relationship via a DNA test between descendents of a a common male ancestor? Like say, between half first-cousins? i.e., my grandfather or his siblings and one of their first cousins...
Quick correction: mtDNA does not require all-female lines, mothers, and only mothers, pass on mtDNA to all of their sons and daughters.
The short answer to your question is yes, it is generally possible. However, it may not be possible in this situation, depending on how the half-siblings are related. The type of DNA testing that they use in paternity tests and crime labs does not rely on mt- or Y-chromosomal DNA; instead, sequences that are known to be highly variable among human beings are used. These sequences mutate faster (more often) than the rest of the genome, such that a predictable number of changes are expected to arise in each generation. If two people have identical, or even highly similar, sequences in these regions of the genome, then the probability that they are not related essentially exceeds the population of the Earth. In other words, there will be something like a 1/15 billion chance that two unrelated individuals would have an identical sequence. (I don't know the exact probabilities, or how much difference can
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I am interested in finding out if one branch of my family is related to another, just because the circumstances concerning my great-grandmother are fishy; my great-great-grandfather was told that he had a kid, so he went back to get my g-grandmother. But how did he know she was his? lol
So my great-grandmother passed on in 1985. She has one half sister still alive, but in the Philippines. Another half-sister died in 2006 but her descendants live in Montreal & Portland so it'd be easier to test them.
My question if it's possible to establish a relationship via a DNA test between descendents of a a common male ancestor? Like say, between half first-cousins? i.e., my grandfather or his siblings and one of their first cousins...
Reply
The short answer to your question is yes, it is generally possible. However, it may not be possible in this situation, depending on how the half-siblings are related. The type of DNA testing that they use in paternity tests and crime labs does not rely on mt- or Y-chromosomal DNA; instead, sequences that are known to be highly variable among human beings are used. These sequences mutate faster (more often) than the rest of the genome, such that a predictable number of changes are expected to arise in each generation. If two people have identical, or even highly similar, sequences in these regions of the genome, then the probability that they are not related essentially exceeds the population of the Earth. In other words, there will be something like a 1/15 billion chance that two unrelated individuals would have an identical sequence. (I don't know the exact probabilities, or how much difference can ( ... )
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