Modern genetics began in 1900 with the rediscovery of Mendel's paper, and now the sequencing of the human genome has brought the first century of progress in this field to a triumphant conclusion. Genetics has entered a new era with the advent of genomic and proteomic approaches, and the knowledge in no other biological discipline is advancing as rapidly as that in molecular genetics and cell biology. Proliferation of new terms inevitably accompanies such exponential growth. The sixth edition of A Dictionary of Genetics addresses the need of students and professionals to have access to an up-to-date reference source that defines not only the most recently coined terms, but in many cases also presents important ancillary encyclopedic information.A Dictionary of Genetics has a broader coverage than its name implies, since it includes definitions of strictly genetic words along with a variety of non-genetic terms often encountered in the literature of genetics. There are about 7,000 definitions, and tables or drawings that illustrate 395 of these. In addition to the main body of the dictionary, this work features new Appendices covering the genomic sizes and gene numbers of about 30 organisms ranging from the smallest known virus to humans, an up-to-date listing of internet addresses for easy access to genetic databanks, and a list of developments, inventions and advances in genetics, cytology, and evolutionary science from the past 400 years. These 900 entries, covering a period from 1590 to 2001, are also cross-referenced in the definitions that occur in the body of the dictionary. No other genetics dictionary supplies definitions cross-referenced to chronology entries or has species entries cross-referenced to an appendix showing the position of each organism in a taxonomic hierarchy. These features make A Dictionary of Genetics the most important lexicon in this field.

The world's foremost geneticist surveys the major developments in what is emerging as the most important single area of scientific inquiry in the twentieth century: biological theory of evolution.

Introduction When the study of heredity and variation first came to be treated as a scientific subject-and this, one must remember, was only just over a hundred years ago-there was an unfortunate separation between the disciplines of cytology and experimental breeding. This separation was based partly on a lack of understanding and partly on a lack of the desire to understand. Even WILLIAM BATESON, the first apostle of mendelism in England, had a blind spot for cytology and for many years dogmatically refused to believe that MENDEL'S determinants were transmitted and distributed by the chromosomes. This separation between cytology and experimental breeding is one which persists, in a measure, even today, simply because there are two quite different, though complementary, techniques available for the study of heredity and variation. On the one hand, one can study directly the structure and behaviour of the actual vehicles which transmit the genetic determinants from one generation to the next. This is the method employed by those who study genetics through a microscope. The alternative method is that used by the experimental breeder who, in default of being able to watch the hereditary factors segregate from each other directly, is obliged to examine the constitution of the germ cells indirectly by sampling, and usually at random, the products of a controlled mating.