Do not taunt Happy Fun Ball (rokeon) wrote in little_details,
Do not taunt Happy Fun Ball

Can DNA testing distinguish sibling vs parent?

I'm trying to figure out if there's actually a story in this- it's kind of pointless to begin writing if the big suspenseful moment at the end will just go *fizz.* Help?

The scenario would be this: teenage girl, newly orphaned, certain things are coming up to make her suspect (correctly) that her parents weren't really her parents. So she steals her older sister's toothbrush, orders a sibling DNA test off the internet, and that's where I don't know what would happen.

The sister would actually be her mother: got pregnant when she was 14, the parents covered it all up and raised the granddaughter as their own. Everything I found says that parents and full siblings are both 50% matches, and mitochondrial DNA would be the same either way. So would the test give a false positive? Or would there be something that would let the lab identify the real relationship?

ETA: I know 50% is only an average for non-identical siblings. I'm wondering what results she would get with only her sister as a comparison.

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