A Boa’s Virgin Birth and a Genetic Anomaly

Never mind, for a second, that a boa constrictor in the US has been confirmed to have undergone two virgin births (which happens in less than 0.1% of all vertebrates — so, two!, holy cow!) for a second.  Which! You know, is pretty amazing.  Like Jesus of Nazareth levels of amazing!

But, what’s really fascinating about the boa’s story, who, despite being held in captivity since 2007 with four male boa’s and decided she’d rather go the whole virgin birth route instead of get knocked up by any of the potential gentleman callers, is that her offspring are actually half-clones of the mother!  Say what? 

Let’s break it down, Gregor Mendel style: “All the offspring also had very unusual sex chromosomes.  Sex chromosomes are packages of DNA that drive the development of sexual characteristics; they essentially make animals genetically male or genetically female.  Humans for example have X or Y sex chromosomes; females have two X chromosomes and males have a combination of an X and a Y chromosome.  In place of X and Y, snakes and many other reptiles have Z and W chromosomes. In all snakes, ZZ produces males and ZW produces females.”

Still with me?  Okay, then.  These snakes had the genetic markup of WW.

But.  And.  The fact that her litters had the WW combination is not that crazy.  It’s been reproduced before in a lab. What’s crazy, is that in all instances of reptilian parthenogenesis the offspring demonstrate ZZ characteristics.  The WW combination was long thought to be un-viable.  Now?  Not so much.

The ramifications of this snake-jesus-mojo isn’t quite clear to scientists at this point, but this discovery of viable WW genetic offspring has upended everything they thought they knew about reptilian reproduction.

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