Despite great efforts in medicine and science, more than 400,000 people worldwide are still dying of malaria. The infectious disease is transmitted by the bite of mosquitoes infected with the malaria parasite Plasmodium. The genome of the parasite is relatively small with about 5,000 genes. In contrast to human cells, Plasmodium parasites only have a single copy of each individual gene. If one removes a gene from the entire genome of the parasite, this leads therefore directly to a change in the phenotype of the parasite.