The pfYC plasmid family exhibits typical behaviour during Plasmodium falciparum transfection, and can be maintained episomally and chromosomally integrated. (A and B) The entire pfYC1xx:FL plasmid series was either transfected individually (A) or as a single pair (pfYC110:FL + pfYC120:RL) (B) under the appropriate drug selection initiated on day 4 post-transfection (arrow). Firefly and Renilla luciferase levels were monitored to assess parasite population growth kinetics until a parasitaemia ≥1% was attained. (C). The copy number of each plasmid per parasite genome was determined for both the single and double transfections. (D) PCR confirmation of chromosomal integration of pfYC320 and pfYC340 at the cg6 locus in the P. falciparum 3D7-attB strain. The β-actin gene was PCR amplified as a positive control.