<p>A. Constructs used for selection of parasites that translate the second open reading frame of the <i>var2csa</i> gene. The drug selectable marker <i>blasticidin-S-deaminase</i> (BSD) was used to select parasites translating the downstream cistron (equivalent to exon I of <i>var2csa</i>). All three constructs also contain the <i>hdhfr</i> selectable marker for maintaining the episomes in transfected parasites prior to blasticidin selection (not shown). B. A drug resistant population appeared after six days suggesting that a subset of parasites is capable of translating the second ORF. Replacing the uORF with <i>Renilla luciferase</i> (V2RB) led to severely retarded growth in presence of blasticidin. Analysis of episomes recovered from these parasites indicated that they had undergone recombination (not shown).</p
