Only one of them, the right-handed form, is teratogenic and causes birth defects.
Biologically important amino acids reaching earth with an enriched abundance of left-handed forms might later have undergone some process of selection that eliminated the right-handed forms.
Only one set of these isomers exists in nature, those derived from the "right-handed form" of glucose, denoted -glucose.
When chemists synthesize amino acids in the laboratory, the result is a mixture of roughly equal amounts of the left-handed and right-handed forms.
A right-handed form of the tau neutrino would bring the number up to four, which is too many.
Z-DNA is quite different from the right-handed forms.
The gyroelongated square bicupola is one of five Johnson solids which are chiral, meaning that they have a "left-handed" and a "right-handed" form.
It exists in both as a chiral isomer, showing both left- and right-handed forms, as well as a meso stereoisomer, which is not chiral.
Amino acids, the building blocks from which proteins and the other chemical ingredients of life are assembled, are chiral molecules that can take either left-handed or right-handed form.
There are both left-handed and right-handed forms, which are mirror images of each other.