chapter 1 Introduction / chapter 2 Overview of Chromosomal Instability and Aging Mechanisms / chapter 3 Cellular Senescence / chapter 4 Telomeric Shortening and Replicative Aging / chapter 5 Telomeric Regulation in Eukaryotic Cells / chapter 6 Role of Ku at the Telomere / chapter 7 Chromosomal Instability in Normative Aging / chapter 8 Chromatin, Aging, and Cellular Senescence / chapter 9 Werner Syndrome / chapter 10.Bloom Syndrome: Genetic, Cellular, and Molecular Features as Compared to Werner Syndrome / chapter 11 Molecular Biology of Rothmund�Thomson Syndrome / chapter 12 Hutchinson�Gilford Progeria Syndrome / chapter 13 Ataxia-Telangiectasia / chapter 14 Nijmegen Breakage Syndrome / chapter 15 Dyskeratosis Congenita / chapter 16 Genetic Instability and Fanconi Anemia / chapter 17 Xeroderma Pigmentosum / chapter 18 Down Syndrome / chapter 19 Genomic Instability and Yeast Aging / chapter 20 Genetics of Aging in the Nematode Caenorhabditis elegans / chapter 21 Aging, Somatic Maintenance, and Genomic Stability in Drosophila melanogaster John Tower -- chapter 22 Telomerase-Deficient Mouse Model / chapter 23 Animal Models of Oxidative Stress and Aging / chapter 24 Conclusions and Future Directions