[Image by Wokandapix via Pixabay and Creative Commons 2.0 License.] 

Imagine you’ve been invited to a fancy dinner at a millionaire’s house. The table is set. The silverware gleams. The guests are chitchating about who does what for work and the season finale of Game of Thrones when the dinner host arrives and announces that he has poisoned himself.

The confusion turns to terror when the dinner party host reveals that he has not only poisioned himself but everyone else in the room.

Such a scenario sounds silly, but if you’re a gene in the game of inheritance, “you win or you die.” (Or at least, risk disappearing from the gene pool.) And sometimes the most extremely “selfish genes” are the ones that survive.

Case in point: Some strains of kombucha yeast, the friendly fungus that makes fermented kombucha tea,  carry a gene called “wtf4“. (Yes. That is its real, technical name.) 

[A jar full of mature kombucha tea. Image via Wikimedia Commons] 

As far as scientists know, wtf4 offers no benefits to its carrier. It doesn’t help kombucha ferment tea leaves or survive refrigeration. It doesn’t boost tendril growth or amp up spore production or even coast along as a neutral passenger. In fact, wtf4 is poisonous to the sex cells (aka “gametes”) of the yeast it lives in. (But not to humans.)

wtf4‘s poisonous nature mainly comes into play during meiosis–the process of typical cells dividing into sex cells with only half the total complement of chromosomes.

Genetics researchers at the Stowers Institute noticed that when yeasts that had just one copy of wtf4 (as opposed to 2 copies) went through meiosis, over 90% of the viable sex cells came out carrying wtf4.

All else being equal, you would expect the sex cells to have a 50-50 chance of inheriting wtf4 from a heterozygous parent. Something was killing off the gametes that didn’t inherit wtf4. 

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