In this book, the authors present new research in the study of sex chromosomes. Topics discussed in this compilation include the evolution of mammalian X chromosomes and X chromosome inactivation; the role of sex chromosomes in mammalian female fertility; the fate of the Y chromosome; the role of Y chromosome genes on tumour development risk in disgenetic gonads; deletion of amelogenin Y-locus; non-invasive prenatal diagnosis for foetal sex determination; and application of X chromosomal STR polymorphisms to individual identification.