Bruce Alberts

As the amount of information in biology expands dramatically, it becomes increasingly important for textbooks to distill the vast amount of scientific knowledge into concise principles and enduring concepts.As with previous editions, Molecular Biology of the Cell, Sixth Edition accomplishes this goal with clear writing and beautiful illustrations. The Sixth Edition has been extensively revised and updated with the latest research in the field of cell biology, and it provides an exceptional framework for teaching and learning. The entire illustration program has been greatly enhanced.Protein structures better illustrate structure–function relationships, icons are simpler and more consistent within and between chapters, and micrographs have been refreshed and updated with newer, clearer, or better images. As a new feature, each chapter now contains intriguing openended questions highlighting “What We Don’t Know,” introducing students to challenging areas of future research. Updated end-of-chapter problems reflect new research discussed in the text, and these problems have been expanded to all chapters by adding questions on developmental biology, tissues and stem cells, pathogens, and the immune system.

For nearly a quarter century Molecular Biology of the Cell has been the leading cell biology textbook. This tradition continues with the new Fifth Edition, which has been completely revised and updated to describe our current, rapidly advancing understanding of cell biology. To list but a few examples, a large amount of new material is presented on epigenetics; stem cells; RNAi; comparative genomics; the latest cancer therapies; apoptosis (now its own separate chapter); and cell cycle control and the mechanics of M phase (now integrated into one chapter). The hallmark features of Molecular Biology of the Cell have been retained, such as its consistent and comprehensive art program, clear concept headings, and succinct section summaries. Additionally, in response to extensive feedback from readers, the Fifth Edition now includes several new features. It is now more portable. Chapters 1-20 are printed and Chapters 21-25, covering multicellular systems, are provided as PDF files on the free Media DVD-ROM which accompanies the book.* And for the first time, Molecular Biology of the Cell now contains end-of-chapter questions. These problems, written by John Wilson and Tim Hunt, emphasize a quantitative approach and the art of reasoning from experiments, and they will help students review and extend their knowledge derived from reading the textbook. The Media DVD-ROM, which is packaged with every copy of the book, contains PowerPoint® presentations with all of the figures, tables and micrographs from the text (available as JPEGs too). Also included is the Media Player, which plays over 125 movies—animations, videos, and molecular models—all with voice-over narration. A new reader-friendly feature is the integration of media codes throughout the text that link directly to relevant videos and animations. The Media DVD-ROM holds the multicellular systems chapters (21-25) of the text as well. By skillfully extracting the fundamental concepts from this enormous and ever-growing field, the authors tell the story of cell biology, and thereby create a coherent framework through which readers may approach and enjoy this subject that is so central to all of biology. * There is also a reference edition of Molecular Biology of the Cell, Fifth Edition (ISBN 978-0-8153-4111-6) that contains Chapters 1-25 entirely in printed format.

Using differential interference contrast optics, combined with cinematography, we have studied the morphological changes that the living, syncytial embryo undergoes from stage 10 through 14 of Drosophila embryogenesis, that is just prior to and during formation of the cellular blastoderm. We have supplemented these studies with data collected from fixed, stained, whole embryos. The following information has been obtained. The average duration of nuclear cycles 10, 11, 12 and 13 is about 9, 10, 12 and 21 min, respectively (25 degrees C). In these four cycles, the duration of that portion of the mitotic period that lacks a discrete nuclear envelope is 3, 3, 3 and 5 min, respectively. The length of nuclear cycle 14 varies in a position-specific manner throughout the embryo, the shortest cycles being of 65 min duration. During nuclear cycles 10 through 13, it is commonly observed in living embryos that the syncytial blastoderm nuclei enter (and leave) mitosis in one of two waves that originate nearly simultaneously from the opposite anterior and posterior poles of the embryo, and terminate in its midregion. From our preparations of quick-frozen embryos, we estimate that these mitotic waves take on average about half a minute to travel over the embryonic surface from pole to equator. The yolk nuclei, which remain in the core of the embryo when the rest of the nuclei migrate to the periphery, divide in synchrony with the migrating nuclei at nuclear cycles 8 and 9, and just after the now peripherally located nuclei at nuclear cycle 10. After cycle 10, these yolk nuclei cease dividing and become polyploid. The syncytial embryo has at least three distinct levels of cytoskeletal organization: structured domains of cytoplasm are organized around each blastoderm nucleus; radially directed tracks orient colchicine-sensitive saltatory transport throughout the peripheral cytoplasm; and a long-range organization of the core of the embryo makes possible coherent movements of the large inner yolk mass in concert with each nuclear cycle. This highly organized cytoplasm may be involved in providing positional information for the important process of nuclear determination that is known to occur during these stages.