The sequence of the human genome is almost completed, and the anatomy of the human genome is now at hand. Within a decade we have advanced from having very little information about the genetic details of biology to possessing an immense amount of structural information on individual genes. The complete genome sequence of humans and many other species provide a new starting point for understanding our basic genetic makeup and how variations in genetic instructions result in human disease or other individual variations.

Genetic researchers are now faced with a very exciting, if not somewhat overwhelming, array of new challenges that may be tackled with existing methodologies, but will most certainly require new and/or updated technologies, altered perspectives and renewed vigor. Seamless collaboration among clinicians, epidemiologists, geneticists, mathematicians and computer experts will be needed to solve the genetic background of complex diseases. The UCLA campus, with expertise ranging from molecular biology to biocomputing, has tremendous potential for leading research in the post-genomic era.

Areas for continued and expanded research in genomics include:

• Lessons from mouse and fly: Information on genes of other species will be of utmost importance when we try to determine functions of human genes. Analyses of well-characterized mouse strains and genetically modified mice will be of greatest significance in this research, since mice and humans share close homology of many gene sequences. Similarly, the fruit fly, due to well-established genetics and experimental possibilities, serves as a valuable model for genome analyses.
• Epidemiological studies: While experimental species are valuable for initial identification and functional analyses of genes, final evidence for the involvement of genes in human diseases must come from extensive epidemiological studies, preferably in different populations. Initial analyses of the completed human sequence suggests that the number of human genes (about 35,000) is lower than expected. However, there are a huge number of individual variations in our genome. So far, we understand next to nothing of the function of these variations and their significance to human health and disease.
• Biocomputing: The gene products - proteins - perform their functions by acting in coordinated networks. Only a fraction of these networks have been identified in the pre-genomic era. Novel biocomputing-based strategies of genome sequences will facilitate identification of new biochemical reactions and all metabolic pathways in the human body, providing new insights into human health and disease and exposing novel targets for drug development by the pharmaceutical industry.

In the post-genomic era, genetic information will be examined in multiple health-care situations throughout the life of an individual. Genetic testing will contain a wide spectrum of analyses with totally different consequences for individuals and their families, depending on the focus and the timing of the testing.

The challenge for health-care professionals will lie in their interpretation and implementation of the outcome of genetic tests. Genetic counseling, explaining the purpose and results of genetic tests, will be crucial in helping individuals to make informed decisions - particularly when test results can only be presented as probabilities. Current training of medical students must be revised to prepare students for these challenges. The fruits of the genome project can only be reaped if the information is used with high professional skills and ethically solid standards to improve life and alleviate suffering.

Leena Peltonen is chair of the Department of Human Genetics and holds the Gordon and Virginia MacDonald Distinguished Chair in Human Genetics.