Touraine AOC and from Sauvignon blanc and Arbois grapes. The white Touraine wines are dry, fairly firm, lively and full, and keep well when bottled. The sparkling wines are allowed to use the designation "Touraine mousse" (sparkling Touraine wine). Up to 20% of Chardonnay grapes may be included in the mixture of varieties grown. The red wines are produced from Cabernet Franc, Cabernet Sauvignon, Côt, Pinot noir, Pinot Meunier, Pinot gris, Pineau d'Aunis and Gamay grape varieties (Gamay is used only for wines marketed in the first year after production). These wines are flavoursome and tannic in character. Touraine wines sold in
Petite mutation Petite mutation petite (ρ–) is a mutant first discovered in the yeast "Saccharomyces cerevisiae". Due to the defect in the respiratory chain, 'petite' yeast are unable to grow on media containing only non-fermentable carbon sources (such as glycerol or ethanol) and form small colonies when grown in the presence of fermentable carbon sources (such as glucose). The petite phenotype can be caused by the absence of, or mutations in, mitochondrial DNA (termed "cytoplasmic Petites"), or by mutations in nuclear-encoded genes involved in oxidative phosphorylation. A neutral petite produces all wild type progeny when crossed with wild type. petite mutations can