Scientists have long known that most compounds in living things exist in mirror-image forms. The two forms are like hands; one is a mirror reflection of the other. They are different, cannot be superimposed, yet identical in their parts.
When scientists synthesize these molecules in the laboratory, half of a sample turns out to be “left-handed” and the other half “right-handed.” But amino acids, which are the building blocks of terrestrial proteins, are all “left-handed,” while the sugars of DNA and RNA are “right-handed.” The mystery as to why this is the case, “parallels in many of its queries those that surround the origin of life,” says Sandra Pizzarello, a research professor at Arizona State University.
An important discovery has been made with respect to the mystery of this “handedness” in biomolecules. Some of the possible abiotic precursors to the origin of life on Earth have been shown to carry “handedness” in a larger number than previously thought.