text: Petite mutants show extranuclear inheritance.The inheritance pattern varying with the type of petite involved.
  Segregational petites (pet–): mutants are created by nuclear mutations and exhibit Mendelian 1:1 segregation.
  Neutral petites (rho–N): Neutral petite when crossed to wild-type, all offspring are wild-type. It has inherited normal mitochondrial DNA from wild-type parent, which is replicated in the offspring.
  Suppressive petites (rho–S): crosses between petite and wild-type, all offspring are petite, showing "dominant" behavior to suppress wild-type mitochondrial function.
  Most petite mutants of S. cerevisiae are of a suppressive type, and they differ from neutral petite by affecting the wild-type, although both are a mutation in mitochondrial DNA. Mitochondrial genome of yeast will be the first eukaryotic genome to be understood in terms of both structure and function and this should smooth the way to understand the evolution of organelle genomes and its relationship with nuclear genomes.It is evident that Ephrussi's work not only opened the field of extrachromosomal genetics, but also provide a fantastic incentive for the investigations which followed up to this day.
  Though S. cerevisiae has been extensively studied in this and other areas, it is difficult to say if the molecular mechanisms of this process in the mitochondrial DNA are conserved across other yeast species.  Other yeast species, such as Kluyveromyces lactis, Saccharomyces castellii, and Candida albicans have all shown to produce petite negative mutants.  Potentially, these yeasts have a different inheritance system in place for their mitochondrial genome than S. cerevisiae does.
  The frequency at which S. castellii spontaneously produces petites is similar to that of S. cerevisiae, with the mitochondrial DNA of those petites being highly altered via deletion and rearrangement. Suppressive petites of S. cerevisiae are the most commonly observed spontaneously created mutants, whereas in S. castellii, the most commonly observed spontaneous mutant is the neutral petite, further leading to speculation that the transference of this mutation differs between species.