Dr. Mark A. Jobling at the University of Leicester published a study in 2005 that examined DYS464, a Y-DNA marker commonly sequenced for genetic genealogical purposes. As it turns out, sequencing DYS464 can inadvertently detect an AZFc deletion. Deletion of AZFc (azoospermia factor c) causes spermatogenic failure and subsequently, male infertility. This marker is tested by at least 6 firms.
Dr. Jobling pointed out that a previous study had concluded that an AZFc deletion could be found in 1 in every 4000 males. In Dr. Jobling’s study there were 3 cases in 3255 males tested, which he states is “not significantly different from 1 in 4000.” A story in the New Scientist stated that “a study by Jobling’s team suggests that 1 in 1000 men has the deletion,” but I think that is an overstatement by the media. I haven’t seen anywhere that Dr. Jobling made such a statement – he was merely listing some of his data. Elsewhere, Ann Turner has suggested that at FTDNA, the number is around 1 in 8,000. Although the exact frequency has not yet been determined, it appears that it is rather low.
The number of markers tested will undoubtedly continue to rise before we cross The Barrier, the move from individual STRs to full-genome sequencing. As a result, the probability that a tested marker could reveal more than just genealogical information will become more and more likely. It is, and always will be, important that individuals be aware of the possible consequences of DNA testing BEFORE they undergo DNA testing. Naturally, this awareness is the responsibility of both the DNA testing firm and the individual.
HT: Hsien, and thank you to the Journal of Medical Genetics for making this paper open access.