Something like a percent of people have neither XX nor XY chromosomes. They have other combinations. The great majority do not know this, unless there is some other reason they wind up getting genetic testing.
For that matter, there are people with XX chromosomes that develop as males, and people with XY chromosomes that develop as females.
When you send your sample off to Ancestry.com or 23andme.com or other such companies, and they find your chromosomes are not typical of people with your reported physical sex, what do they tell you? People doing these tests are generally not preparing themselves for news of this type, but there must be tens of thousands of customers who would be in this category.
They probably just tell them the unvarnished facts. They are adults sending off their samples so that they can learn the truth, not fragile little hothouse flowers that need to be patronized like bunny rabbits.
I am doubtful that any such companies run a karotype. It is not clear that their routine testing would be capable of detecting many, if not most, sex chromosome variants. I would think they are simply running cleaved DNA against a large variety of markers. That does not lend itself well to known the physical arrangement of the chromosomes.
I think most of them do Y chromosome ancestry, so they’d have to at least do enough karotyping to find a Y. Though they might skip that for a customer who identifies as female, and they might not count the number of Xs.
The FDA regulates what the testing companies can tell you about your DNA. The list of acceptable reports is always being updated. The companies also give you a choice as to whether or not you see the allowed reports and if you do choose to see, say, your Parkinson’s markers, they walk you through the ramifications of knowing pretty thoroughly.
That being said I don’t know if X-Y anomalies are reported. But they wouldn’t just be sprung on anyone.
No need to run a karotype to run a Y chromosome ancestry. A karotype requires laboriously scanning cells under a microscope to find one in the process of duplication that still has its chromosomes spread out enough that they do not appear overlapping from the microscope’s view. It is a huge pain to do and avoided if at all possible.
Checking a haplogroup type (Y chromosome ancestry) can be done with some simple probes that are not more complicated that testing other genetic loci. But such tests very well may not detect the presence of an extra Y chromosome. Similarly testing on a loci on the X chromosome may not detect an abnormal number of X chromosomes in a person.
First off, this most common abnormalities are quite easily detectable by next-generation sequencing, which is what these companies use for these tests. If you’re, say, heterozygous for Y chromosome markers, or heterozygous for X chromosome markers and also positive for Y chromosome markers, that will jump out at you pretty quickly.
I work in the clinical genetics world - doing these sorts of tests, but for medical conditions, not for fun. If something like this popped up in our lab, we would generally feel like we had a duty to report it to the ordering physician, because depending on the condition, it has a good chance of being medically relevant. We’d generally have our genetic counselors call and explain what we found.
I’m not sure what the regulations or industry standards are for recreational testing. I’d look through the fine print for language about how they handle “incidental findings”.
