The "Symposium on Aneuploidy: Etiology and Mechanisms" was held at the Carnegie Institution of Washington Auditorium from March 25-29. 1985. This Symposium developed as a consequence of the concern of the Environmen­ tal Protection Agency with the support of the National Institute of Envi­ ronmental Health Sciences about human exposure to environmental agents that cause aneuploidy. The program was chosen to explore what is currently known about the underlying causes, the origins, and the extent of the prob­ lem of human aneuploidy, and whether exposure to environmental agents is assodated with an increased incidence of aneuploidy in humans. Basic research findings in the area of mitosis and meiosis were presented and related to possible mechanisms of how aneuploidy may be produced spontane­ ously and chemically. A survey of data regarding the chemical induction of aneuploidy in experimental organisms was presented. Outstanding scientists from different fields were invited to cover a broad perspective of aneu­ ploidy from the molecular aspects to the human situation. We hope that the publication of the proceedings will share the enthu­ siasm of the meeting and its scientific content. The topic of aneuploidy has received little attention and it is the purpose of this Volume to establish a scientific basis for assessing health risks posed by environ­ mental exposures to aneuploidy-inducing chemicals. Vicki L. DeJlarco Peter E. Voytek Alexander Hollaender vii ACKNOWLEDGEMENT The Editors of the proceedings of the "Symposium on Aneuploidy" wish to acknowledge the support of Dr. Elizabeth L.

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Introduction: Assessment of Health Risks..- Human Aspects.- I: The Impact of Aneuploidy.- The Impact of Aneuploidy Upon Public Health: Mortality and Morbidity Associated with Human Chromosome Abnormalities.- Down Syndrome: Economic Burdens and Benefits of Prevention..- Economic Costs of Aneuploidy: Some Problems of Measurement and Conceptualization.- II: Etiological Aspects of Human Aneuploidy.- Meiotic Investigations of Aneuploidy in the Human.- Chromosomal Abnormalities in Human Sperm.- The Origin of Aneuploidy in Humans.- Maternal Age, Paternal Age, and Human Chromosome Abnormality: Nature, Magnitude, Etiology, and Mechanisms of Effects.- Genetic Factors Influencing Aneuploidy Frequency.- Environmental Causes of Aneuploidy: Why So Elusive?.- III. Neoplasia.- Neoplasia and Cytogenetic Abnormalities.- IV: Roundtable Discussion.- Human Aspects of Aneuploidy.- Mechanisms Underlying Chromosome Disjunction/Nondisjunction.- I: Chromosome Movement and Distribution.- Mitosis in Eukaryotic Cells: An Overview of Chromosome Distribution.- Spindle Structure and the Mechanisms of Chromosome Movement.- Characterization of a Tightly Centromere-linked Gene Essential for Meiosis in the Yeast SaccharomycesCerevisiae.- The Kinetochore of Mammalian Chromosomes: Structure and Function in Normal Mitosis and Aneuploidy.- Microtubule Dynamics and the Mitotic Cycle: A Model.- Aneuploidy Induction by Mitotic Arrestants in Animal Cell Systems: Possible Mechanisms.- A Model for the Mechanism of Aneuploidy Involving Chromosome Displacement.- Discussion: Perspectives and Future Directions Regarding the Mechanisms of Aneuploidy.- II: Meiotic Mechanisms and Their Consequences on Chromosome Distribution.- Molecular Biology of Meiosis: Synapsis-associated Phenomena.- The Meiotic Process and Aneuploidy.- The Synaptonemal Complex in Meiosis: Significance of Induced Perturbations.- The Role of Mobile DNA Elements in Unequal and Intrachromosomal Crossing-over in DrosophilaMelanogaster.- Noncomplementation Phenomena and Their Bearing on Nondisjunctional Effects.- Experimental Approaches for the Detection of Chromosomal Malsegregation Occurring in the Germline of Mammals.- Research Needs in Meiosis, Mechanisms of Synapsis, and Chiasma Regulation.- Maternal Aging as the Important Etiological Factor in Human Aneupioidy.- Mechanisms of Nondisjunction: Facts and Perspectives.- Mechanisms and Detection of Chromosome Malsegregation Using Drosophila and the Yeast SaccharomycesCerevisiae.- Current Status of Aneuploidy Testing.- Special Committee Report, Part I: An Evaluation of Current Testing Approaches for the Detection of Chemically Induced Aneupioidy.- Special Committee Report, Part II: Quantitative Evaluation of Chemicals that Induce Aneupioidy Using the Genetic Activity Profile Method.- Chemical Probes and Possible Targets for the Induction of Aneupioidy.- Mechanisms to Stimulate Research on Assay Systems to Detect Aneupioidy.- Future Directions in Test System Development and Validation.- Role of Aneupioidy in Early and Late Stages of Neoplastic Progression of Syrian Hamster Embryo Cells in Culture.- Etiology and Mechanisms of Aneupioidy: A Synopsis.- Index of Organizing Committee, Chairmen, Speakers, Special Discussants, and Participants.