That’s when it began to become clear that Ethan was a little unlike other boys and men before him, who have all inherited a Y chromosome from their fathers. Though rare, it’s not unheard of for a child who is genetically a girl to develop as a boy when a very small piece of Y chromosome that contains a region called SRY (which stands for sex-determining region Y) is inherited. When this happens, a person’s entire course of development can be shifted toward the male road instead of the female one.
In search of this little piece of SRY, the next step we employed in Ethan’s case was called FISH (fluorescence in situ hybridization). The FISH test involves using a molecular probe that binds only to parts of the chromosome that are complementary.
What we expected to see in Ethan was that the FISH for the SRY region would be positive, as it is in other cases that present in this way. But it wasn’t. In fact, it’s not only that Ethan didn’t inherit a Y chromosome from his father, he didn’t even get a microscopic trace of one. And that didn’t leave us with many known genetic explanations as to how Ethan could have turned into a boy.
Actually, according to the genetics textbook sitting on my desk, he really should have been a girl.
. . . For a very long time the dogma has been that while chromosomally we may be male or female, developmentally we all start out the same. If we inherit a Y chromosome, or even a very small part of it, we take a detour toward maleness. In the absence of that, though we’d all continue to head down the genetic path of being a female.
But in Ethan, as we saw, that wasn’t the situation. So we began to suspect that the conventional genetic wisdom was indeed wrong.
. . . What I am suggesting, however, is that our sexual biology isn’t just about genetic sex, but rather the unique combination of genes, timing and the environment. As we keep seeing, people who fall away from the norm, for whatever reason, have a lot to teach the rest of us.
That’s not just the case for the one-in-a-billion cases like Ethan, but also for hundreds of millions of people around the world who don’t conform, genetically, biologically, sexually, or socially, to the rigid and traditional view of masculinity and femininity.
– Inheritance by Sharon Moalem, MD, PHD