Walker and her team showed that the color of grape skins is controlled by two genes, VvMYBA1 and VvMYBA2. They found that either gene can regulate the color by switching on production of a molecule called anthocyanin, which turns grape skin red. In white grapes, both the genes are mutated, meaning both ways for producing a red color are switched off.
“This was a lucky coincidence for all the white wine drinkers around the world,” Walker said. “Mutations in single genes happen at a fairly low frequency, but the grapes had to have mutations in two genes to turn from red to white and that’s just very, very rare.”
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