There are specific proteins that code for specific qualities or functions and do so since they are formed like the letter "I" more so than they are formed like the letter "T." Because the shapes of these particles exist in either a left-handed or right-handed fashion, these researchers surmised that they might produce alien life based upon the human genome, except that every place there was a human left-handed particle, a matching yet similar right-handed "mirror-image" particle would be developed and utilized in its location. The same concept would be used for existing human particles that exist in the right-handed fashion. If we exist in either the right-handed or left-handed form (and we do), why couldn't other beings exist as our specific mirror images?

appliedbiocorp.com