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Given the DNA of a parent and the DNA of a child of the parent, is it possible to tell which DNA belongs to the parent and which to the child? I've tried looking this up online, but could only find information on paternity tests, and about differentiating the DNA of a parent from the DNA of a sybling, given the DNA of some individual.

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    – Carey Gregory
    Aug 15, 2022 at 19:41
  • Dear Carey, is this sufficient?
    – domotorp
    Aug 15, 2022 at 20:08
  • Do you have any additional information about the two individuals or just two samples of extracted genomic DNA? Can you provide additional context? You may find this article interesting.
    – Ian Campbell
    Aug 15, 2022 at 20:10
  • @Ian My question's motivation is purely theoretical. Given my very limited biological knowledge, I see no way to differentiate, so I wonder whether I've missed something. Also, let us consider looking at telomere lengths cheating, I only want to focus on the genetic information.
    – domotorp
    Aug 15, 2022 at 20:21
  • I'm a little unsure what you meant in your response to @IanCampbell. Did you mean "chaining" instead of "cheating?" Telomere length is genetic information, so if you're saying you don't want to consider it, I don't understand why since it directly addresses your question.
    – Carey Gregory
    Aug 16, 2022 at 0:04

1 Answer 1

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There is one case where you might be able to differentiate parent and child, taking advantage of the fact that mitochondrial DNA is only inherited from the mother.

If one genome is female and the other male, but the mitochondrial DNA are almost identical, then the male genome is that of the child and the female genome is the parent. If the mitochondrial DNA are different, and you definitely know that the samples are from one parent and one child, then the male genome would be the parent, and the female genome would be the child.

If both genomes are male, and the mitochondrial DNA are different, you haven't learned anything. If the mitochondrial DNA are the same, you've learned that they can't be parent and child.

If both genomes are female and the mitochondrial DNA are the same, you haven't learned anything. If they are different, you've again learned that they can't be parent and child.

Generally though I think you are going to need a trio of samples to be able to distinguish parent from child (two parents and a child or one parent and two siblings).

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  • Just what I was looking for! One final question: if both are male, they could be parent and child, with some not so far common ancestor in the maernal lineage, right?
    – domotorp
    Aug 18, 2022 at 4:52

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