10 Developmental Genetics of the Germ Line

Abstract

I. INTRODUCTION
The function of the germ line is to produce specialized cells, sperm, and oocytes, whose union results in the production of a new individual. Germ cells differ fundamentally from somatic cells: They undergo a specialized cell cycle, meiosis, in which haploid gametes are formed following genetic recombination and chromosome re-assortment; they are toti-potent, as their descendants will form every tissue in the individual; and they are immortal in that they will give rise to progeny with a new germ line, thus ensuring continued propagation of genetic information.

The study of germ-line development addresses a number of issues, some of which are specific to germ cells, whereas others relate to general aspects of biology. How is the germ-line lineage specified as distinct from somatic lineages? How is sexual identity determined? How is proliferation controlled? How is the decision to exit the mitotic cycle and enter the meiotic pathway made? What activities control the transitions between different stages of meiotic prophase? How are the specialized gametes formed? How are meiotic prophase progression and gametogenesis coordinated? How are the development and function of the germ line and somatic gonad coordinated?

Research by the Caenorhabditis elegans community addressing these questions is reviewed here. Additional features of germ-line development are described in other chapters in this volume: recombination and meiotic divisions (Albertson et al.), programmed cell death (Hengartner), spermatogenesis (L’Hernault), and fertilization (Kemphues and Strome).

II. SUMMARY OF ANATOMY AND DEVELOPMENT OF THE GERM LINE
The development of the reproductive systems in the...