Twin Paternity Test Thought Experiment?

Question

OK, I thought of this at work today. What  if there were two sets of identical twins, one male and one female, and they each married each other (so each male twin has a female twin bride) and then both sets of twins get pregnant and give birth around the same time(yes, it's unlikely, but it could happen right?)?  Would the DNA tests of both babies come back positive for both sets of parents? I know twin DNA is nearly identical(http://www.wonderquest.com/twins-dna.htm) and it makes me wonder would you be able to tell which twins were the parents of the babies off of DNA tests or would they come back as too close to call? If anyone else has actually thought about this I'll be amazed, but I am really curious about it. Any help is appreciated.

Leut. Dan Taylor · Accepted Answer

It's not really a thought experiment.

Twins have identical DNA (as far as these tests would be concerned). No paternity test would be able to figure out who's child is who's.

The same would go for the much simpler case, a set of twins both sleeps with a woman, you couldn't use paternity results to determine which was the father.

science teacher · Answer

While it is true that identical twins have married identical twins, and that they do seem to have children at the same time, there is the factor that for every trait, it takes 2 sets of genes. So when sperm or eggs are made the set of 2 splits and some sperm or egg get one part of the set and others get the other. This is especially important for traits that are heterozygous, meaning that they show dominant but have the recessive gene in the background. They can repair in any combination. Not every child of a fmaily looks alike.

Frank N · Answer

Identical twins result from the division of a single fertilized egg.  Barring mutations, identical twins have identical DNA.  But not all children from a single pair of parents are identical.  In rare cases, fraternal twins have very similar DNA.  The two babies you describe did not come from the same egg, so they are not identical twins.  The chances they have similar DNA are exactly the same as any non-identical siblings from the same parents.

Twin Paternity Test Thought Experiment?

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