inF.A.Q. for 23andMe: what if I have mitochondrial DNA from Pa?

Have you ever asked any important but infrequently asked questions? Have you ever heard about the first personal genome service by the biotech startup 23andMe? Here is an inF.A.Q. addressed to this company:

According to the cool 23andMe genetics educator:

maternal mitoDNA

According to the peer review literature this is not necessarily the case and sometimes (rarely I admit) things in your cells can happen otherwise or more scientifically (mitochondrial recombination can occur):

paternalmtDNA

When 23andMe’s Maternal Ancestry Tree service is tracing the genetic path of their customers, the microarray employees are identifying their haplotypes based on the differences in the mitochondrial DNA. The company is using SNPs (single nucleotide variants) unusually both from genes in the compact mitochondrial coding region (around 15.5kb) as well as within the circa 1kb large hypervariable region to give a detailed ancestry assignment. 23andMe examines few thousand places (over 2000 says Mr. Bettinger) on the mitochondrial DNA out of the total 600,000 SNPs.

But.

In the above case the 28 year old man’s blood and muscle differed at 18 positions which allowed assignment of the two sequences to separate European mtDNA haplogroups, H and U5, former being the same as the mother’s haplotype, while the haplotype of the patient’s muscle mtDNA was identical to that of his father’s and uncle’s blood. I wonder whether 23andMe’s Illumina chips can help make things clear in cases like this. (solution: let’s sequence the whole mito genome instead of a couple thousand basepairs). So as the first step in my mission to support the mission of 23andMe to support the mission of academic research I’d like to suggest putting a short tail on the possibility of paternally inherited mtDNA in the cool 23andMe genetics education material. Even if this could lead to the little confusion of some costumers, but otherwise will satisfy the experts. Chance is that the website of 23andMe will become a dominant tool of public genetics education in the future and that involves a growing responsibility on behalf of the editors there to give correct and detailed scientific information.

P.S. PR article used: Schwartz M, Vissing J.: Paternal inheritance of mitochondrial DNA. N Engl J Med. 2002 Aug 22;347(8):576-80. PMID: 12192017

4 thoughts on “inF.A.Q. for 23andMe: what if I have mitochondrial DNA from Pa?

  1. Of course full sequencing is where they’re headed (they’ve said as much) because that would allow them to uncover more complex mutations like BRCA1, but it’s not at the $1000 price point just yet.

  2. Pingback: A Round-Up of Discussions Following the Launch of deCODEme and 23andMe » The Genetic Genealogist

  3. Good post.

    Chance is that the website of 23andMe will become a dominant tool of public genetics education in the future and that involves a growing responsibility on behalf of the editors there to give correct and detailed scientific information.

    Prominent biologist John Maynard Smith was co-author in a paper in Science (286[24 December 1999]:2524-2525) which opens with,

    The assumption that human mitochondrial DNA is inherited from one parent only and therefore does not recombine is questionable…

    This assumption has been used extensively to date events in human prehistory, including the age of our last common female ancestor, “Eve”, and the spread of Homo Sapiens in Asia and Europe

    The paper is titled, “Linkage Disequilibrium and Recombination in Hominid Mitochondrial DNA”.

    Maynard Smith commenting on that particular paper told the New Scientist (178 [14 July 2000] 48) that he

    is frustrated but not surprised that the establishment chooses to ignore these findings.

    It’s been almost 8 years since the Maynard Smith paper so do you think his frustration is valid?

    If paternal mtDNA transmission occurs how much of a wrench would it throw into the data gathered with the assumption that mtDNA is only transmitted through the mother?

    Personally I think it throws a huge wrench which is why I think the “establishment chooses to ignore these findings”.

  4. Yes, the paternal inheritance is considered as a taboo topic sometimes on behalf of the status-quo scientists and it is really a very disruptive assumption (that’s why I like it from a scientific point of view.) Here is one status-quo paper:

    Bandelt et al., “More evidence for non-maternal inheritance of mitochondrial DNA?

    “Objective: To find potential instances of non-maternal inheritance of mtDNA.

    Methods: Published medical case studies (of single patients) were searched for irregular mtDNA patterns by comparing the given haplotype information for different clones or tissues with the worldwide mtDNA database as known to date—a method that has proved robust and reliable for the detection of flawed mtDNA sequence data.

    Results: More than 20 studies were found reporting clear cut instances with mtDNAs of different ancestries in single individuals. As examples, cases are reviewed from recent published reports which, at face value, may be taken as evidence for paternal inheritance of mtDNA or recombination.

    Conclusions: Multiple types (or recombinant types) of quite dissimilar mitochondrial DNA from different parts of the known mtDNA phylogeny are often reported in single individuals. From re-analyses and corrigenda of forensic mtDNA data, it is apparent that the phenomenon of mixed or mosaic mtDNA can be ascribed solely to contamination and sample mix up.”

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