The pattern of mutations provides identification of the probable geographic origin of a CQR isolate. The number of mutations apparently required for CQ resistance explains two riddles, namely, why CQ resistance took so long to appear on a large scale and why it had been impossible to create CQR strains from CQS strains in the laboratory via drug selection. However, if one begins with Sudan 106/1, a strain that harbors all but one of the mutations required to complete a CQR-pfcrt allele, CQR strains can be rapidly created in the laboratory by CQ selection [57] , and the final mutation required to complete the CQR-pfcrt allele [55] is found in these selected strains. In performing this experiment, Cooper et al. also found PfCRT substitutions that are not known to exist in the wild but that confer unusual and scientifically informative drug-resistance profiles [57] .