Sister Chromatid Exchanges 25 Years of Experimental Research Part A: The Nature of SCEs

Chromosomes. being well-defined structures that are easily vis­ ible under the optical microscope. readily lend themselves to in­ tense physical and biochemical study. The understanding of the structure and function of this most critical genetic material has progressed through a number of interesting stages. Often connected with the development of new techniques in staining and photography. using the standard microscope and the electron microscope. It is interesting to look back at the history of cytogenetics. I would like especially to emphasize the work of Karl Sax and many of his students. Work with Tradescantia became feasible after Edgar Anderson straightened out the ecology and Sax took advantage of the small number of chromosomes easily visible under the microscope. As a matter of fact. this development is seen as the foundation for the quantitative analysis of radiation effects on chromosomes. During the 50 years since then.- more refined studies have been initiated. The study of cytogenetic mechanisms has become an important tool for the recognition of the effects of environmental factors on all liv­ ing systems and has made SCE studies possible. One of the most important stages in chromosome research was the development, in radiation biology, of radiolabeling the chromosome with tritiated thymidine. This technique. published in 1957 by Dr.

of Part A.- Historical Perspective.- A Brief History of the Discovery of Sister Chromatid Exchanges.- Detection, Significance, and Mechanism of Sister Chromatid Exchange Formation: Past Experiments, Current Concepts, Future Challenges.- The Nature of SCEs.- Spontaneous and Halogenated Pyrimidines.- Probing Sister Chromatid Exchange Formation with Halogenated Pyrimidines.- The Replication of Unsubstituted and 5-Bromodeoxyuridineor 5-Chlorodeoxyuridine-Substituted DNA Regulates the Rate of Induction of Sister Chromatid Exchanges.- Indiction of DNA Lesions, Chromosomal Aberrations, and G2 Delay by Bromo- and Chlorodeoxyuridine.- BrdUrd-Independent and BrdUrd-Dependent SCEs as Components of SCE Yields: Implications for Their Cellular Significance.- Ring Chromosomes and Sister Chromatid Exchanges.- Cytogenetic Characterization of the Chinese Hamster Ovary Mutant EM9.- High Induction of Sister Chromatid Exchanges and Chromosome Aberration by 5-Bromodeoxyuridine in a Ethylmethanesulfonate-Sensitive Mouse Lymphoma Cell Mutant (ES 4).- Induction and Characterization of SCEs.- Activated Oxygen Species at the Origin of Sister Chromatid Exchanges.- Induction of Sister Chromatid Exchanges in Split-Dose and Cell-Fusion Experiments.- Thymidylate Stress and Sister Chromatid Exchanges.- Sister Chromatid Exchange and DNA Methylation.- Cell-Stage Dependence of the Formation of SCEs and Chromosomal Aberrations.- Sister Chromatid Exchange (SCE) Induced by Laser-UV- Microirradiation: Correlation Between the Distribution of Photolesions and the Distribution of SCEs.- Persistence of SCE-Inducing Lesions In Vivo: Relevance to Mechanisms of SCE Formation.- DNA Damage Persistence and Site Specificity in SCE Formation.- The Contribution of DNA Single-Strand Breaks to the Formation of Chromosome Aberrations and SCEs.- Replication Bypass SCE Mechanisms and the Induction of SCE by Single-Strand Adducts or Lesions of DNA.- Modulation of SCE Induction.- The Effect of Cell Proliferation, Bromodeoxyuridine Concentration, and Deoxynucleoside Triphosphate Pools on Sister Chromatid Exchange Induction.- Effect of Bromodeoxyuridine on Induced Sister Chromatid Exchanges.- The Mechanism of 3-Aminobenzamide-Mediated Increases in Spontaneous and Induced SCEs.- DNA Repair and Sister Chromatid Exchanges.- Potentiation of Induced Sister Chromatid Exchanges and Chromatid-Type Aberrations by Inhibitors of DNA Synthesis and Repair in G2.- The Action of Anticlastogens on Chemically Induced SCE.- Enchancement of Carcinogen-Induced Chromosome Breakage and Sister Chromatid Exchange by 13-Cis-Retinoic Acid.- Correlations.- The Induction of SCE with Relation to Specific Base Methylation of DNA in Chinese Hamster Cells by N-Methyl-N-nitrosourea and Dimethylsulfate.- Relationships Between Specific DNA Adducts, Mutation, Cell Survival, and SCE Formation.- Interrelationships of SCEs, Mutation at the HGPRT Locus, and Toxicity in Chinese Hamster V79 Cells.- The Induction of Sister Chromatid Exchanges by Environmental Pollutants: Relationship of SCE to Other Measures of Genetic Damage.- The Quantitative Comparison Between SCE and Transformation Frequencies Induced by Chemical Carcinogens in Syrian Hamster Cells.- Quantitative Predictivity of Carcinogenicity for Sister Chromatid Exchanges In Vivo.- Statistical Analysis.- Statistical Design, Analysis, and Inference Issues in Studies Using Sister Chromatid Exchange.- Guidelines for the Statistical Evaluation of SCE.- Statistical Evaluation of Sister Chromatid Exchanges: Refined Method.- Statistical Analysis of High SCE Frequency Cells in Human Lymphocytes.- A Statistical Analysis of Neanthes arenaceodentata, Sister Chromatid Exchange Data.- Participants and Speakers.