Friday, September 06, 2013

It's a girl! Maybe

I'm a sucker for Panda Cams, especially ones involving baby pandas.

But this statement by Brandie Smith, the National Zoo’s senior curator of mammals and giant pandas, raised alarm bells in my mind.
“Females have two X chromosomes,” Smith said. “Males have an X and a Y chromosome. So we actually look at the chromosomes. It wasn’t physical identification of gender. There is room for error with that.”

“If you look at the chromosomes, there’s no mistake,” she said. “So that’s the way to go. Go to the cellular level.”
If pandas are anything like humans, there is room for error with both methods.

Does anyone else remember the brouhaha during the Olympics about gender checks? At first, athletes dropped their pant(ies) in front of physicians. That was considered too demeaning so they switched to chromosome tests. That led to much drama and pain as athletes who were raised as girls suddenly discovered that they had XY chromosomes.

I read in the Olympic coverage at the time that the XY chromosome test fails in approximately a in 500 people. Gene expression is highly comples. Sometimes, if the Y chromosome is damaged, the X can compensate. So people who have XY chromosomes can present outwardly as females. 

Apparently,  XY females retain some Y chromosomal athletic advantages; they are over-represented among elite female athletes.  One physician said that, at every Olympics, several women discover that they are XY.  Not only do are they disqualified from competition, but they face gender identity crises at  a highly public and stressful time.

As a humane gesture, the Olympics switched back to the visual checks.

I did a bunch of searching among the internets and found Erroneous Gender Identification by the Amelogenin Sex Test. Pay attention to the paragraphs at the end:
The occurrence of this phenomenon has been reported as an 0.018% observed sex test failure rate in the Austrian National DNA database (9), 1.85% observed sex test failure rate in Indian males (10), 0.6% frequency of sex test failure attributable to deletion from 350 specimens from all around the world (11), and 8% (2 out of 24) samples of unrelated Sri Lankan males (11).

With the finding of our first mistyped amelogenin result on a male out of a total of 96 samples, we can report the failure rate of this test as 1.04% in Israel. Moreover, the failure of two different primer sets, to amplify the Y chromosome DNA, suggests that this sample contains a deletion in the relevant area.
The bibliography gives details of the earlier studies.  The Austrian National DNA database study, published in 2002 (about the time I read about the change in Olympic rules), matches the 1 in 500 failure rate.  However, it looks like the number could be as high as 1 in 50!

Anyway, no test is perfect.  And some things in life are just ambiguous.  Would I want to compete athletically against XY women?  No more than I want to compete against people who are bigger, stronger, faster, receive better coaching/training or put in more practice time than me.  But, you know what?  Isn't the spirit of amateur competition to put your best out there and let the better player win?

I know that panda is gonna be super-cute, regardless of gender.

National Zoo Panda cam link.


  1. an interesting and educational post! i had no idea there were so many genetic tests done in sports. hmm...

  2. that is incredibly interesting! I didn't realise they had gone back to the "drop the panties" test, but it does seem to be a less humiliating and traumatic option given the precedent.


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