petite mutants

A class of yeast mutants, most studied in Saccharomyces cerevisiae. Mutants grow slowly and rely on anaerobic respiration: mitochondria, although present, have reduced cristae and are functionally defective (termed promitochondria). There are three types of petite mutant: (i) Segregational mutants that show Mendelian behaviour and result from mutations in mitochondrial genes located in the nucleus; (ii) Neutral petites, which are recessive genotypes and result from the complete absence of mitochondrial DNA; (iii) Suppressive petites, in which most of the mitochondrial DNA is lost (60-99%), though what remains is often amplified.