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DNA of Semyon

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RMK:

--- Quote from: tenne on February 26, 2023, 12:27:01 PM ---"A study of chromosomal (nuclear) DNA allows you to establish kinship only at a very close genetic distance: parents and children, siblings.

This is an inaccurate statement from an expert. kinship can be determined down to 6th cousins by the amount of shared DNA. While the nuclear DNA would not say great great niece, it would give the amount of shared DNA and that would be used to determine how close he was to the other person. The fact that he stated it wouldn't, and he is an expert, makes me very suspicious of his test results


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--- End quote ---
tenne, you are correct that DNA can be used to determine how closely two people are related, even if they are distant relatives.  Stated precisely, DNA can tell you what proportion of segregating alleles two people have in common, identical-by-state (IBS). I expect some of the meaning in the scientist's words was lost in translation.  Specifically, I suspect what was translated as "kinship" refers to the exact form of the familial relationship between two people; it seems that WinterLeia understood it that way, too.  When you read the scientist's quote with that interpretation, what he says is true, per the chart you posted yourself.  If two people share 33% or more of their segregating alleles IBS, then they pretty much have to be a parent-offspring pair, or full sibs (or, monozygotic twins!).  Further, a parent-offspring pair will always share exactly 50% of segregating alleles IBS (except for rare scenarios, like uniparental disomy).  Since parent-offspring and full-sibling relationships are the least ambiguous to infer from IBS proportions, they are the most useful in constructing a pedigree (a "family tree", if you like) from DNA, which I believe is the point WinterLeia was trying to convey.  More distant familial relationships are much harder to nail down if all you have is the two individuals' DNA samples, which is evident from that chart.  For example, if two people share 18% of their segregating alleles IBS, it is within the realm of possibility that they could be any of the Group B or Group C types of relatives.

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