<<Print>>

Scientists have created mosquitoes that produce 95% male offspring, with the aim of helping control malaria. Flooding cages of normal mosquitoes with the new strain caused a shortage of females and a population crash. The system works by shredding the X chromosome during sperm production, leaving very few X-carrying sperm to produce female embryos. In the wild it could slash numbers of malaria-spreading mosquitoes, reports the journal Nature Communications. Although probably several years away from field trials, other researchers say this marks an important step forward in the effort to produce a genetic control strategy. Malaria is transmitted exclusively by mosquitoes. Despite reductions brought about by measures such as nets or spraying homes with insecticides, it continues to kill hundreds of thousands of people annually, mostly in sub-Saharan Africa. The idea of using a �sex-distorting� genetic defect to control pest populations was proposed over 60 years ago, but this is the first time it has been practically demonstrated. The researchers, led by Prof Andrea Crisanti and Dr Nikolai Windbichler of Imperial College London, transferred a gene from a slime mould into the African malaria mosquito Anopheles gambiae. This gene produces an enzyme called an �endonuclease� which chops up DNA when it recognises a particular sequence.