FIG 1.

Diagram illustrating the principle of a malaria genetic cross of rodent malaria parasites. A cross starts with an intravenous or intraperitoneal injection of blood samples containing gametocytes from two parasite strains (in this case, Plasmodium yoelii subsp. nigeriensis N67 and P. yoelii subsp. yoelii 17XNL, that have different growth characteristics and virulence in mice). Mice infected with mixtures of gametocytes are anesthetized and fed to Anopheles stephensi mosquitoes. Approximately 15 to 17 days after feeding, the infected mosquitoes with salivary gland sporozoites are allowed to feed on new mice. Daily blood smears are made to monitor parasitemia. The resulting parasites are cloned through limiting dilution by injecting a single parasite into a mouse or are frozen in liquid nitrogen for future studies. The parasite mixtures can be also used for linkage group selection (LGS) after applying selection pressure such as drugs.