UK scientists who decoded a third of the human genome say their next target will be the zebrafish.

They will use the genetic data from the colourful animal to help them decipher the functions of human genes.

The work could shed light on common human birth defects and a host of other health problems, including those of the heart, blood and nervous system.

The three-year project will be carried out at the Sanger Centre, just outside Cambridge, in an initiative that will again be funded by the Wellcome Trust medical research charity.

Lab model

The humble zebrafish, like the mouse and the fruit fly, has long been used as a model for human health in laboratory studies.

Its genetic material, or genome, is about half the size of our own. The zebrafish has similar blood, kidney and optical systems to that of humans.

Michael Dexter, director of the Wellcome Trust, said in a statement: "This builds on the seminal work, supported by the Wellcome Trust, on the human genome sequencing project and will help all our future studies on gene function, leading to health care benefits."

And Nobel prize-winning scientist Christiane Nusslein-Volhard from the Max-Planck Institute, Germany, added: "Zebrafish is the ideal organism to study the function of human genes."

Other animals

Once the genetic sequence of the zebrafish is known, scientists will be able to make changes to the animal's DNA to study how human inherited diseases might arise. Some mutations have already been identified in zebrafish that are similar to human blood disorders.

International scientists announced this year, to great acclaim, that they had succeeded in completing the first, rough draft of the human genome. But much of the information gleaned from the "code of life" is meaningless unless there is something with which it can be compared.

Hence there is a drive to read the genetic material of several other animals. The mouse genome, which is the focus of efforts by two rival groups of scientists, is close to completion. The entire fruit fly genome is already available on digital disk for reference.

The dog and the chicken genomes are making slow progress. Some scientists are also calling for an international effort to decode the DNA of man's closest living relatives: the great apes.