Introduction

Diverse disorders of sexual development exist in man, many of them having been recognised since ancient times and indeed some of them conferring on their possessors positions of dubious privilege in society (Fig. 7.1). Whilst scientific description of the disorders has tended to focus primarily on the condition of the gonads, and may find expression in the external genitalia and non-reproductive tissues, the disorders in fact stem from genetic anomalies involving the chromosome complement or perhaps even individual genes. Such anomalies were first critically analysed in the 1950s with the development of reliable methods for karyotyping and, with the ever increasing sophistication of techniques culminating in those at the molecular level, so the precision of diagnosis has increased. One outcome of the cytogenetic or molecular genetic approach has been the revelation that sexual disorders are frequently a consequence of errors at meiosis in the maternal or paternal germ cell line. Another is the realisation that errors in man usually have their counterparts in laboratory rodents and sometimes also in the large farm animals (see Chapters 5 and 6).