Experimentelle Embryologie.

Eggs of all animals contain mRNAs and proteins that are supplied to or deposited in the egg as it develops during oogenesis. These maternal gene products regulate all aspects of oocyte development, and an embryo fully relies on these maternal gene products for all aspects of its early development, including fertilization, transitions between meiotic and mitotic cell cycles, and activation of its own genome. Given the diverse processes required to produce a developmentally competent egg and embryo, it is not surprising that maternal gene products are not only essential for normal embryonic development but also for fertility. This review provides an overview of fundamental aspects of oocyte and early embryonic development and the interference and genetic approaches that have provided access to maternally regulated aspects of vertebrate development. Some of the pathways and molecules highlighted in this review, in particular, Bmps, Wnts, small GTPases, cytoskeletal components, and cell cycle regulators, are well known and are essential regulators of multiple aspects of animal development, including oogenesis, early embryogenesis, organogenesis, and reproductive fitness of the adult animal. Specific examples of developmental processes under maternal control and the essential proteins will be explored in each chapter, and where known conserved aspects or divergent roles for these maternal regulators of early vertebrate development will be discussed throughout this review. Table of Contents: Introduction / Oogenesis: From Germline Stem Cells to Germline Cysts / Oocyte Polarity and the Embryonic Axes: The Balbiani Body, an Ancient Oocyte Asymmetry / Preparing Developmentally Competent Eggs / Egg Activation / Blocking Polyspermy / Cleavage/ Mitosis: Going Multicellular / Maternal-Zygotic Transition / Reprogramming: Epigenetic Modifications and Zygotic Genome Activation / Dorsal-Ventral Axis Formation before Zygotic Genome Activation in Zebrafish and Frogs / Maternal TGF-β and the Dorsal-Ventral Embryonic Axis / Maternal Control After Zygotic Genome Activation / Compensation by Stable Maternal Proteins / Maternal Contributions to Germline Establishment or Maintenance / Perspective / Acknowledgments / References

Wendy Pfeffer describes the amazing metamorphosis from tiny, jellylike egg, to little fishy tadpole, to great big bullfrog. Holly Keller has created the archetypal frog pond and we see it through the seasons as the tadpoles grow legs and lungs and eventually hop onto land: bullfrogs at last. "Well-designed ink drawings washed with soft-toned watercolors stretch across the double-page spreads, showing the action above and below water level. . . .an attractive, general introduction."—BL. 1994 "Pick of the Lists" (ABA) Best Children's Science Books, 1994 (Science Books and Films)

How tiny variations in our personal DNA can determine how we look, how we behave, how we get sick, and how we get well. News stories report almost daily on the remarkable progress scientists are making in unraveling the genetic basis of disease and behavior. Meanwhile, new technologies are rapidly reducing the cost of reading someone's personal DNA (all six billion letters of it). Within the next ten years, hospitals may present parents with their newborn's complete DNA code along with her footprints and APGAR score. In Genetic Twists of Fate, distinguished geneticists Stanley Fields and Mark Johnston help us make sense of the genetic revolution that is upon us. Fields and Johnston tell real life stories that hinge on the inheritance of one tiny change rather than another in an individual's DNA: a mother wrongly accused of poisoning her young son when the true killer was a genetic disorder; the screen siren who could no longer remember her lines because of Alzheimer's disease; and the president who was treated with rat poison to prevent another heart attack. In an engaging and accessible style, Fields and Johnston explain what our personal DNA code is, how a few differences in its long list of DNA letters makes each of us unique, and how that code influences our appearance, our behavior, and our risk for such common diseases as diabetes or cancer.