Sounds like mother & father's nuclear DNA, injected into the nucleus of a 3rd party's donor's egg cell, which contains its own mitochondrial DNA. Since mtDNA is normally inherited 100% from the mother (since the mother's egg cell supplies the mitochondria to the embryo), if the mother has a mitochondrial genetic disease, 100% of her children would normally inherit it.
Notably, this prevents transmission of a disease that is "fatal to any baby conceived", which makes this as uncontroversial a case of a "designer baby" as I can imagine. After this, the ethics get much more complicated.
If I'm understanding correctly, this could be used for cloning if you could select two nuclei with non-overlapping chromosomes from a single person's sperm/eggs ... much easier to clone a man due the limits of egg extraction.<p>back of the envelope:<p>- each gamete has 1 of 2 choices for 23 chromosomes.<p>- you need to find any two non-overlapping<p>- probability of non-overlap is 0.5^23 for any pair<p>- number of pairs equals (n choose 2) where n is number of gametes = n!/ (2 * (n - 2)!) = 0.5 * n * (n-1) = 0.5 * (n^2 - n)<p>- to get a 50/50 chance of finding the right gametes: 0.5 = 0.5^23 * 0.5 * (n^2 - n), which is equivalent to: 0 = 0.5^23 * (n^2 -n) - 1<p>- solved via wolfram alpha, you would need to screen 2897 nuclei non-destructively to get a 50% chance of being able to generate a clone.<p>I'm not aware if this is possible or not. But obviously if you can just replace chromosomes in-nucleus that is easier than screening, but if you can do that you don't really need this whole process since you can just replace the nucleus after IVF. If you could harvest a sex cell and do meiosis in a test tube, that would also get you your nuclei right away as well -- from 10 seconds of googling, I don't think we have this yet.<p>I think when they screen zygotes they do it after some replication has happened, so the math really works against you if you need to combine sperm+egg pre-screen because you don't get the birthday paradox effect if you have to commit to your pairings beforehand, you'd need to huge egg supply as well.
Additional background info from last year:<p><a href="http://www.bbc.com/news/health-31594856" rel="nofollow">http://www.bbc.com/news/health-31594856</a>
> But the science does raise ethical questions, including how any child from the technique might feel about having DNA from three people.<p>That's not an ethical problem. Also, not a problem since, it's not any kind of problem to consider how kids might like PB&J sandwiches either.
the original story, with more detail, is here <a href="https://www.newscientist.com/article/2107219-exclusive-worlds-first-baby-born-with-new-3-parent-technique/" rel="nofollow">https://www.newscientist.com/article/2107219-exclusive-world...</a>
Note that this will not stop some kids from getting these type of diseases, collectively known as mitochondrial myopathies.<p>Some of them arise sporadically [1]<p><pre><code> In chronic progressive external ophthalmoplegia (CPEO) — a myopathy with the defining features of ophthalmoplegia and ptosis — Δ-mtDNAs are found only in muscle (implying that the deletion event occurred after fertilization in the muscle lineage of mesoderm).
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How do I know ? I have a mitocondrial myopathy (CPEO). My mother was perfectly healthy and all my brothers and sisters (5) are also ok.<p>[1] <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3959762/" rel="nofollow">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3959762/</a>
mtDNA is also very significant in historical migration studies... if anyone has a high level explanation of the global state of knowledge in this area I would love to see it ... trying to author a regionally focused ancient history book and piecing together the disparate pieces of supposed genetic evidence for various things is a task I am wholly unqualified for and would love some assistance with.