petite mutation

petite (ρ-) is a mutant first discovered in the yeast Saccharomyces cerevisiae. Due to 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.