Open Thread – December 11th, 2010

By Razib Khan | December 11, 2010 10:13 am

Weird story about twin brothers contesting paternity, Who’s Your Daddy? Paternity Battle Between Brothers:

“With identical twins, even if you sequenced their whole genome you wouldn’t find difference…they’re clones,” said Dr. Bob Gaensslen, a forensic scientist at Orchid Cellmark labs in Texas. “There are a few things in science that are cut and dried and this is one of them.”

Dr. Bob Giles, a paternity testing expert, agrees. “There is simply no test that explains the difference between two identical twins,” he said.

Is this right? Their sperm should have different distinctive mutations by this time in their lives, right? Which would be passed on to the child.

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  • biologist

    There’s probably no commercially available test that can decide this. However, there probably are informative mutations. The problem is that there may not be that many of them.

    Whole-genome sequencing could be used to identify candidate mutations the differentiate the brothers. You could then confirm them with genotyping. If enough informative mutations were found, they could determine paternity.

    Ideally you’d like to find a mutation that occurred after the split of the two brothers so that it affects all or most of one brother’s somatic and germ cells but not the other’s. Later mutations would be harder to work with owing to greater mosaicism. Mutations that occurred during spermatogenesis leading to the daughter are likely inaccessible.

  • Gio

    I’m very interesting on the identical twins issue for philosofical reasons , and if the twins differ only in epigenetic and not in original genome, like recent works show, this has a lot of implications about our identity and not least about the cloning issue.

  • dan

    @#2 – damn you! i wanted to believe at least someone could finally live the dream. a tag team with zero inhibition.

  • Rachel

    This whole problem isn’t a new legal dilemma. Its the way all paternity cases used to be until 100 years ago. We didn’t get anything close to certainty until about 30 years ago. So there’s plenty of reliable case law to use resolving the dispute.

  • http://washparkprophet.blogspot.com ohwilleke

    The 50-50 solution resembles that of hunter-gatherer tribes where paternity is kept deliberately ambiguous so that all men in the tribe have an interest in raising the children of the tribe.

    The possibility of simply honoring the birth certificate designation has the virtue of being Solomanic. The mother presumably names the man she feels is most worthy, and given the lack of genetic differences, worthiness to be a father as determined by the mother may produce the outcome that is most beneficial from a practical perspective for the child.

  • Matt B.

    I wouldn’t expect consistent mutation in the sperm, i.e. not all the sperm from one twin would have the same mutations, since most of the accumulation of mutation would have happened after the testicles became fully developed. One ejaculation might not produce more than a few dozen identical sperm for all I know, and that’s not counting the variation in which of each pair of chromosomes they have. So you might be able to find a slight statistical difference between the twins based on whole semen samples, but you might not be able to match that to the one sperm that produced the child, which should have very few of the total number of mutations.

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This blog is about evolution, genetics, genomics and their interstices. Please beware that comments are aggressively moderated. Uncivil or churlish comments will likely get you banned immediately, so make any contribution count!

About Razib Khan

I have degrees in biology and biochemistry, a passion for genetics, history, and philosophy, and shrimp is my favorite food. In relation to nationality I'm a American Northwesterner, in politics I'm a reactionary, and as for religion I have none (I'm an atheist). If you want to know more, see the links at http://www.razib.com

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