Fig. 4. Flow cytometry analysis of transgenic T. gondii expressing histone 2b-YFP and stained with Hoechst 3342. Two-dimensional scatter plot showing fluorescence in the YFP and Hoechst channels, on an arbitrary scale with logarithmic detection. Forward scatter intensity and pulse width, and side scatter intensity were used as gates to discriminate between intact single parasites (85.3% of 1.6x10⁵ total events) and cell debris or multiple parasites in a cluster. Discrete peaks for haploid parasites are clearly observed: 1N DNA content, 94% of the parasite population (red background region) and 2N DNA content, 5.4% of the population (green background). A small number of parasites with DNA content 3N (0.1%, yellow background) are also present.