An ambitious experiment (2005)

Key Experiments in Practical Developmental Biology details influential experiments in the field for undergraduate or postgraduate students to replicate in the laboratory class. The editors have set themselves an ambitious goal. Many of the experiments in this book are, as suggested by the editors, straightforward. For example, some of the crosses and phenotypic analyses described require care and good microscopes, but no tremendous manipulative skill. Students may be asked to set up a cross then determine,for example, the bristle numbers on a fly notum, or petals and sepals on an Arabidopsis flower. Of course, such experiments do require that one can obtain and maintain all the special strains that are cited. I had expected that the fly strains used in this book would be standard ones available from the Bloomington Stock Center; however, many are not, so presumably the authors of such chapters would need to provide them.Beyond setting up the experiments, many of the techniques that are described here, although in standard use in a research lab (such as in situ hybridization to embryonic mRNAs), are still unreliable in a teaching lab. Perhaps the editors should have insisted that their authors use procedures that adapt well to undergraduate exercises. For example, the X-gal staining of lacZ reporter strains is a technique that usually works well, and it is exploited in this book in some instances. But even when lacZ reporter strains are available, such as those for studying early gene expression in blastoderm-stage fly embryos, the author of a particular chapter still suggests that in situ hybridization is used, without making clear the disadvantages of X-gal staining.Beyond some of the genetic crosses and analyses, there are several well-designed and straightforward drug applications, such as the application of retinoids to amphibian limbs or to fish embryos, and some straightforward surgery or dissociation experiments. However, the chapters often turn to things that I cannot imagine trying with even a small class. Having taught both undergraduate lab courses and advanced classes in embryology at Cold Spring Harbor and the Marine Biological Laboratory at Woods Hole, I believe it would be rash to expect most of these experiments to be feasible in a university class setting. Even if a lab were well equipped with microscopes,manipulators and first-class facilities for a variety of animals, many of the manipulations are just plain difficult, and particularly so if there has been no skilled demonstration beforehand. By all means, examine the fates of dissociated sea urchin blastomeres, but if any student can do a micromere transplant in an undergraduate class, the instructor should insist that they switch immediately to honors research. Even if a lab class can obtain growth factors to put onto beads, the technique of bead implantation into chick embryos takes considerable skill and practice, and the description in this book is no substitute for a demonstration; in inexperienced hands, these experiments have a negligible success rate. Of course, one wants students to gain insights into the nature of understanding by doing experiments and seeing the reality and limitations of generating empirical data, but experiments need to be designed to give students a reasonable shot at success.Although the book frequently aims too high, it is still a useful read for students. The methods are spelled out somewhat more clearly than in the primary literature, and the reader achieves more sense of an experiment than from a developmental biology textbook. In the book, each experiment is introduced, with the materials outlined along with preparation work for staff. Then the experiment is described step-by-step, and finally the expected results are discussed, as are the likely causes of failure. Alternative exercises and teaching concepts are given at the conclusion of each chapter. Thus, even the technically challenging experiments provide useful material for discussion, even though an experienced instructor would be needed to turn them into feasible laboratory exercises.One hesitates to turn a lab class into spectator sport, but the book would be wonderful if accompanied by a DVD of demonstrations. Perhaps then the students could be content with watching how experiments are carried out, and only perform some of the more straightforward exercises. There are also some obvious gaps in the book's content. Lineage tracing in embryos is about as straightforward, yet rich in interpretation and discussion, as other more-detailed manipulations, but it is not discussed in useful detail. And as for grafting, I would like to have seen some experiments that use the experimental embryologist's mainstay: the amphibian embryo.Is there a solution to designing high-level experiments for undergraduates?If the facilities are there, then the best solution exploits the expertise of the local instructors. They can carry out the demonstrations and design an experiment that works at least half of the time in inexperienced hands.