Interregional differences undermine sperm trend conclusions.

Environmental Genome Project. Issues such as these should be carefully considered and addressed during the early stage of the project. As noted at the beginning of the Environmental Genome Project symposium , the project is evolving and is a work in progress. As with any evolving program, it will continue to be molded by new ideas, information, and technologies. The goal of the initial phase of the Environmental Genome Project is to stimulate research in the area of polymorphism discovery. This phase of the project does not specifically seek to assign polymor-phism frequency. An allele has to be present only once in the repository to be discovered , yet accurately estimating the frequency of an allele in different ethnic groups requires genotyping of large numbers of individuals. Once polymorphisms (or alle-les) have been discovered, study groups can be held to consider the research required for assignment of allele frequency. While the Environmental Genome Project does not seek to assign allele frequencies, we are aware of the importance of accurate allele frequency estimates for future epidemiolog-ic studies and the large sample sizes such estimates will require. It is important to consider whether the sample size selected by the Environmental Genome Project will provide sufficient power to discover most alleles relevant to gene-environment interactions. Clearly, sampling 500 to 1,000 individuals will be adequate to identify many new polymorphisms. As pointed out during the symposium, sampling this number of individuals is adequate to identify most of the polymorphisms occurring commonly in the U.S. population. All of the newly identified polymorphisms will have the potential to be involved in gene-environment interactions, although none of them will be guaranteed to be so involved. It is also clear that various combinations of alleles may uniquely collaborate in environmentally associated disease. These allele combinations will, of course, be present in the population at lower levels than each allele alone. As was clearly pointed out at the Environmental Genome Project symposium , studies of gene-environment or gene-gene interactions will require very large sample sizes. Planning for both the technical means of rapid genotyping and the large number of samples for future epi-demiologic studies is a key component of the Environmental Genome Project. Parascandola mention the potential usefulness of the archived lymphocyte cell lines from the NHANES III study and they suggest that this collection has not been explored as a resource for DNA samples. In fact, NHANES III …