Mutant/mutation
The mutant expresses a mutated form of DNA polymerase delta catalytic subunit; the two amino acid residues (D311, E313), known to be critical for the proofreading activity of S. cerevisiae DNA polymerase-δ, are mutated to alanine

Protein (function)
In eukaryotic organisms, the spontaneous mutation rate is very low, e.g. 3.3X10^-10/basepair (bp)/cell division in yeast, 2.7 x 10^-9/bp/generation in C. elegans, and 5.8 x 10^-9/bp/generation in D. melanogaster. The mutation rate of in vitro P. falciparum culture was recently reported as 1.0–9.7 x 10^-9/bp/generation.

DNA polymerases α, δ, and e are involved in nuclear genome DNA synthesis, of which polymerases δ and e possess a proofreading 3' to 5' exonuclease activity for lagging and leading DNA strand replication, respectively.

Disruption of the proofreading activity by site-directed mutagenesis significantly increased  mutation rate in yeast by as much as 10-fold to >100-fold, and the mutator effect is particularly strong in DNA polymerase δ.Furthermore, in microorganisms such as yeast and fungi, the mutator system has been employed to generate various mutated phenotypes including drug resistance

Phenotype
High-throughput genome sequencing analysis revealed that two PbMut lines had 175–178 mutations and a 86- to 90-fold higher mutation rate than that of a control parent line (PbCtl line).

Additional information
A control P. berghei line with wild-type (non-mutated) DNA polymerase δ (referred to as PbCtl) was generated.

PbMut and PbCtl parasites were maintained by weekly passage in ddY mice for 122 weeks. High-throughput genome sequencing analysis revealed that two PbMut lines had 175–178 mutations and a 86- to 90-fold higher mutation rate than that of a PbCtl line. PbMut, PbCtl, and their parent strain, PbWT, showed similar course of infection.

Other mutants