[anorwell]

I think the homochirality of amino acids might be what you're referring to:

https://en.wikipedia.org/wiki/Chirality_(chemistry)#In_bioch...

"The origin of this homochirality in biology is the subject of much debate.[12] Most scientists believe that Earth life's "choice" of chirality was purely random, and that if carbon-based life forms exist elsewhere in the universe, their chemistry could theoretically have opposite chirality. However, there is some suggestion that early amino acids could have formed in comet dust. In this case, circularly polarised radiation (which makes up 17% of stellar radiation) could have caused the selective destruction of one chirality of amino acids, leading to a selection bias which ultimately resulted in all life on Earth being homochiral."

[dekhn]

I've also heard some scientists say that parity breaking could explain the origin of homochirality. Personally, I'm happier with the "random chance" hypothesis.