The generation of genetic mosaicism has mystified, moved and exercised the
minds of many. In recent decades advances have been made that have
significantly contributed to our understanding of how genetic alterations might
generate cellular diversity together with the diversity of cellular behaviour so
characteristically displayed by neoplastic cells. Not only has an array of
alterations been identified but also a larger picture has emerged of genetic
recombination as an important means of producing the panoply of phenotypic
properties. This is the general compass of coverage in this book and therefore
it is in the nature of things that the discussion should cover embryological
phenomena of cell differentiation and morphogenesis, neoplastic disease and
its progression as well as a number of genetic disorders, through which runs
the common strand of genetic instability and variation.