Open Questions: Developmental Biology

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Prerequisites: Molecular biology and genetics

Introduction

Embyology

Evolutionary developmental biology

Recommended references: Web sites

Recommended references: Magazine/journal articles

Recommended references: Books

Introduction

Some of the most astounding phenomena known to science occur so commonly that we've all experienced them and take them for granted. Yet until very recently, they were totally mysterious, and even now present a large number of important open questions.

Developmental biology is all about the astonishing fact that complex multicellular organism consisting of as many as hundreds of trillions of specialized cells are able to develop from one single fertilized zygote.

Certainly, we now know, all the information necessary to specify every type of cell is present in the identical DNA contained in each cell. But the question is: what is the program that directs the use of this DNA information, and how does it work?

Here are some more specific questions about the process:

What triggers cell differentiation?
How do cells specialize?
Can cell specialization be reversed?

Recommended references: Web sites

Site indexes

Virtual Library: Developmental Biology: Part of the WWW Virtual Library.
Open Directory Project: Developmental Biology: Categorized and annotated links. A version of this list is at Google, with entries sorted in "page rank" order. May also be found at Netscape.
Yahoo Developmental Biology Links: Annotated list of links.
Galaxy: Developmental Biology: Categorized site directory. Entries usually include descriptive annotations. More here.

Sites with general resources

The Virtual Embryo: An outstanding site containing many resources for students and researchers in developmental biology. Most of the content is in the part called Dynamic Development, which is entitled "A Modular Resource to Facilitate Learning in Developmental Biology". Some of the best features are the tutorial, the learning resources, and the research resources. But there's a lot more than that. This is the kind of site that every field of science should be so fortunate to possess. The site was originally developed by Leon Browder, co-author of a popular textbook entitled Developmental Biology.
The Visible Embryo: The main feature of the site is a visual presentation of the human embryo and information about it at each of the first 23 weeks after conception and every second week thereafter. Other features include external links, a glossary, and a chat system. Some other features are available to paid subscribers.
Zygote: Site provided by Scott Gilbert to supplement his popular textbook, Developmental Biology (not the same one as Leon Browder's). Contains a wealth of technical information. Includes external links that are keyed to chapters in his book.
Biology Project: Developmental Biology: Part of the University of Arizona Biology Project. There are external links and a tutorial on developmental mechanisms.
Development@nature.com: A portal to relevant Nature Publishing Group resouces in the field of developmental biology.
Society for Developmental Biology: Contains news & information, educational resources, membership services.

Surveys, overviews, tutorials

Category: Developmental biology: Topic category from Wikipedia.
Developmental biology: Article from Wikipedia. See also Evolutionary developmental biology, Homeobox.
Developmental Biology Tutorial: An excellent tutorial that should be one of the first destinations for anyone who wants to understand what developmental biology is all about. Part of the Virtual Embryo site.
Evolutionary Developmental Biology: A ScienceWeek "symposium" consisting of excerpts and summaries of articles from various sources.
Developmental Biology: Complete online textbook, by Scott F. Gilbert. Index. Part of the NCBI Bookshelf.
Developmental Biology Tutorial: Good tutotrial, but limited to narrow focus on human development, located at the Biology Online site.
Embryo Images: Normal & Abnormal Mammalian Animal Development: Presents a tutorial on mammalian embryology using scanning electron microscope images.
The Multi-dimensional Human Embryo: Provides a three-dimensional image reference of the human embryo based on magnetic resonance imaging. Site also has external links and references to additional information.
Developmental Biology Cinema: Short videos on topics in developmental biology.
The Interactive Fly: Interactive tutorial on the developmental biology of the fruit fly.
What Controls Nerve Growth?: Detailed Science Notes article by Anil Ananthaswamy on nerve cell development and regeneration.
Two become one: September 20, 2001 article from Nature concerning the increasing interaction between developmental biology and cell biology.
Of Goethe, genomes and how babies are made: February 10, 2000 article from Nature concerning evolutionary developmental biology.

Recommended references: Magazine/journal articles

Telltale Heart
Jessa Netting
Science News, July 7, 2001, pp. 13-15: The heart is the first organ to develop in the embryos of vertebrates. The genes that control this process are being identified.
[References]
How the Body Tells Left from Right
Juan Carlos Izpisúa Belmonte
Scientific American, June 1999, pp. 46-51: All vertebrates are asymmetric in the way certain internal organs like the heart are situated. This development is controlled by genes which are expressed on only one side of an embryo.
How Limbs Develop
Robert D. Riddle; Clifford J. Tabin
Scientific American, February 1999, pp. 74-79: A protein named "Sonic hedgehog" has been found to be the chemical signal that establishes the anterior-posterior axis of an embryonic limb. This finding has implications for studies of cancer and birth defects.
Gradients that Organize Embryo Development
Christane Nüsslein-Volhard
Scientific American, August 1996, pp. 54-61: Studies of fruit fly embryos have shown some of the basic mechanisms of early embryo development. Concentration gradients of certain proteins acting as DNA transcription factors seem to play the main role.
The Genetics of Flower Development
Elliot M. Meyerowtiz
Scientific American, November 1994, pp. 56-65: Flowers consist of four types of organs -- sepals, petals, stamens, and carpals. It turns out that all are just modifications of leaves, produced by different patterns of gene expression. How the position of a cell within an organism affects gene expression is just beginning to be understood.
The Molecular Architects of Body Design
William McGinnis; Michael Kuziora
Scientific American, January 1994, pp. 55-66: Very similar genetic mechanisms -- HOM/Hox genes -- govern the development of all animal body plans. Such highly conserved genetic mechanisms must have evolved in the first animals, more than 600 million years ago.

Recommended references: Books

Sean B. Carroll – Endless Forms Most Beautiful: The New Science of Evo Devo
W. W. Norton & Company, 2005: There have been a number of books on evo devo for scientists or readers with a good background in biology. This is the first that is truly for a general audience, and given Carroll's stature in the field, it can't fail to be recommended to a wide audience. In the first part, developmental biology is explained as the way animals of all types develop from embryos to adults. Evolution is tackled in the second part, as the way that biological development came to be the way we find it.
[ Book review]
Adam S. Wilkins – The Evolution of Developmental Pathways
Sinauer Associates, 2002: Wilkins gives us an introductory text book for evo devo – "the place where developmental biology and evolutionary biology intersect". It is technical, but not at all beyond the ability of a science-oriented reader to enjoy. The first part covers the foundations, and explains how the history of development can be inferred from fossil evidence. The second part presents case studies in pathway evolution. Conundrums and open questions in the subject are examined in the third part.
Eric H. Davidson -- Genomic Regulatory Systems: Development and Evolution
Academic Press, 2001: Davidson's career has been focused on understanding how the development of an organism is encoded in its DNA and how, as a result, animal evolution unfolded. The book gives a thorough and rigorous account of what he has learned. It assumes some understanding of the molecular biology of gene expression without going into detail. One is stimulated to wonder about the evolutionary steps that led the process of gene expression to work the way it does.
Sean B. Carroll; Jennifer K. Grenier; Scott D. Weatherbee -- From DNA to Diversity: Molecular Genetics and the Evolution of Animal Design
Blackwell Science, 2001: In this work we have a masterful synthesis of molecular genetics, developmental biology, and evolutionary theory. This 3-fold synthesis is one of the most important features of contemporary biology. The presentation is technical but enlivened with numerous colorful diagrams and illustrations. Important topics such as the Hox family of homeobox-containing genes are well explained.
John Tyler Bonner -- First Signals: The Evolution of Multicellular Development
Princeton University Press, 2000: The author adopts an evolutionary perspective on developmental biology by focusing on key initial steps in the evolution of multicellular organisms, through an examination of signaling between cells in slime molds. The book is brief, and the presentation is sophisticated but not overly technical.
Enrico Coen -- The Art of Genes: How Organisms Make Themselves
Oxford University Press, 1999: This is a very good introduction to developmental biology, and it makes no assumption that the reader has any background in biology. It's also nearly the only recent such introduction, and would rate even higher if the painting metaphor weren't pressed quite so hard. Nevertheless, it makes very clear how development takes place, not as a set of explicit instructions, but rather as an implicit "program" of sequential gene expression, guided by proteins produced earlier in the sequence and distributed in a 3-dimensional pattern throughout the developing embryo.
Walter J. Gehring -- Master Control Genes in Development and Evolution: The Homeobox Story
Yale University Press, 1998: Evolutionary theory, molecular biology, and developmental biology have come together in a fascinating synthesis which exposes how the mechanisms that control gene expression have evolved, and how the traces of this evolution remain in the way that the sequence of gene expression governs the development of individual organisms. Gehring, whose laboratory discovered the "homeobox genes" which play a key role in this synthesis, provides an excellent account of his research, full of details and real meat.
Wallace Arthur -- The Origin of Animal Body Plans: A Study in Evolutionary Developmental Biology
Cambridge University Press, 1997: A synthesis of molecular biology, developmental biology, and evolutionary theory is just coming about. Arthur's book is an excellent survey of this emerging synthesis. Although a good deal of technical terminlology is used, the material is mostly accessible to general readers.
John Gerhart; Marc Kirschner &nadash; Cells, Embryos, and Evolution
Blackwell Science, 1997: This weighty textbook is unmistakably intended for serious readers who want to learn the details of how molecular biology, cellular biology, and evolutionary biology interact. The main issue it confronts is to understand how members of a given species can undergo nonlethal heritable variations upon which evolution can act.
Rudolf A. Raff -- The Shape of Life: Genes, Development, and the Evolution of Animal Form
University of Chicago Press, 1996: Raff offers a good, technical presentation of evolutionary developmental biology for specialists, but without excluding dedicated general readers. The emphasis is on the fossil record and systematics, with little treatment of molecular aspects.
Lewis Wolpert -- The Triumph of the Embryo
Oxford University Press, 1992: How, in detail, an embryo can develop from a single cell to a complex organism with hundreds of types of cells is one of the central questions of biology. Wolpert is a master of the field of developmental biology, and presents a beautiful account of the subject in this classic book for general readers.

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