9/2/09!1!Biology 624 - Developmental Genetics!Lecture #3 - Gametogenesis and Fertilization !Gametogenesis-!-the formation of GERM CELLS that will go !on to form progeny-!1. Begins during embryogenesis!2. Involves several steps that ! are independent of sex!3. Continues with sex-specific! processes (ie differ between egg! and sperm)!Germ cell competence!Germ cell specification!Germ cell migration!to gonads!Sperm-egg contact!Spermatogenesis!-results in motile gamete with!haploid DNA content!Oogenesis!-results in relatively!large gamete with!nutritional and !informational molecules!Sperm-egg fusion!Development initiates!Specification of Mammalian PGCs!Segregation of P-granules into the Germ Line"Lineage of the C. elegans Embryo!Segregation of P-granules into the Germ Line"Lineage of the C. elegans Embryo!9/2/09!2!The Pole Plasm of Drosophila!Maternal Effect Genes!Localization of Germ Cell-Less Gene Products in the Posterior of the Egg and Embryo!Inhibition of Transcription in Germ Cell Precursors of C. elegans!Inhibition of Transcription at Ectopic Sites in Drosophila by germ cells-less!Hoechst!GCL! H5 staining!WT + GCL!WT!Leatherman et al (2002) Curr Biol 12, 1681-1685!Pathway for the Migration of Mammalian Primordial Germ Cells!9/2/09!3!Pathway for the Migration of Mammalian Primordial Germ Cells!The Modification of a Germ Cell to Form a Mammalian Sperm!The Ovarian Follicle of Mammals!The Formation of 16 Interconnected Cystocytes in Drosophila!In Amphibian Oocytes, Lampbrush Chromosomes are Active During First Meiotic Prophase!The Formation of 16 Interconnected Cystocytes in Drosophila!9/2/09!4!Specifying the Anterior-Posterior Axis of the Drosophila Embryo During Oogenesis!Specifying the Anterior-Posterior Axis of the Drosophila Embryo During Oogenesis!Formation of the Anterior-Posterior Axis of the Drosophila Embryo!Events Leading to the Fusion of Egg and Sperm Plasma Membranes!Wave of Calcium Release across Sea Urchin Eggs During Fertilization!Possible Mechanisms of Egg