A team of researchers at the University of Wisconsin-Madison and New York University has produced the first, large-scale map of the parasite's genetic material.

Scientists still have to identify the individual genes in the parasite's DNA and the proteins they produce, but the map should greatly speed up the international project to reveal the genetic secrets behind malaria. The ultimate goal is to develop novel ways of combating a disease that has shown a frustrating ability to become resistant to current drugs.

Malaria is a public health problem in some 90 countries, and causes between 1.5 and 2.7 million deaths globally each year. Ninety per cent of all malaria cases are in sub-Saharan Africa where it is the main cause of death and a major threat to child health. Worldwide, a child dies of malaria every 30 seconds.

The most dangerous form of malaria is caused by the single-celled parasite Plasmodium falciparum, which is spread from infected to healthy people through mosquitoes. Decoding the parasite's DNA and identifying all its genes is the goal of the international Malaria Genome Consortium.

The genome of P. falciparum consists of 14 chromosomes. Each of these is made up of a very long stretch of DNA, the molecule that carries the genetic code.

Shotgun technique

Scientists hunt for genes by chopping up the DNA into smaller, overlapping segments. In conventional genome mapping, these fragments are separated in gels, the genetic code deciphered, with the whole jigsaw eventually pieced back together to give a complete picture.

But the Wisconsin-New York team has used a new mapping technique, often referred to as "optical mapping" or the "shotgun" method.

In this, the DNA is "pinned down" on plates and cut up in situ. A laser technique and special software is used to pick out important markers and measure the size of the fragments.

Optical mapping can be done in a fraction of the time it takes conventional methods. It is an automated process that creates a single, complete snapshot of a genome with very small amounts of material.

Assembling the final jigsaw puzzle, knowing where all the genes are supposed to sit on the chromosomes, is one of the most difficult steps of any sequencing project, but it is made much easier if a map of the genome is available.