A single nucleotide polymorphism in the DNA polymerase gamma gene of Saccharomyces cerevisiae laboratory strains is responsible for increased mitochondrial DNA mutability.

In the Saccharomyces cerevisiae strains used for genome sequencing and functional analysis, the mitochondrial DNA replicase Mip1p contains a single nucleotide polymorphism changing the strictly conserved threonine 661 to alanine. This substitution is responsible for the increased rate of mitochondrial DNA point mutations and deletions in these strains.