There was that one day in 1997 when Carole P. Meredith, a UC Davis Professor, and John Bowers, a doctoral candidate in genetics, found the origin of the Cabernet Sauvignon grape.
Using DNA Profiling, the two discovered Cabernet Sauvignon's origin while building a database of genetic signatures found in California.
For years, grapevine varieties have been identified by physical features of their leaves and fruit. Yet these traits can vary according to terroir, so it's not perfect.
If you want to learn more about the two types of DNA fingerprinting they used, restrictive fragment length polymorphism (RFLP) and polymerase chain reaction (PCR), and see how they did it - see this paper on the subject.
In the old world of France, wine grapes would grow wild. According to Meredith and Bowers, Cabernet Franc and Sauvignon Blanc vines spontaneous crossed between adjacent vineyards in the wild and then out popped the Cabernet Sauvignon grape. If fact, the word "sauvignon" is French for "wild."
A close link between Sauvignon Blanc and Cabernet franc has been suspected all along, but without proof there's only speculation. No one had any idea that Sauvignon blanc was related to Cabernet Sauvignon until the DNA tests were completed by Meredith and Bowers.
According to the historical literature we now have access to, Cabernet Franc was mentioned much early in history books than Cabernet Sauvignon.
To experienced wine drinkers, Cabernet Sauvignon can smell like Sauvignon Blanc or Cabernet Franc.
So these facts back up the finds from Meredith and Bowers.
There you go. The mystery can be put to bed now.
Next time you are slurping some dark, black-currant Cabernet, with a smell of green bell peppers, give a little thought to where your wine came from.