Developmental biology or embryology (Greek εμβρυολογία) is the study of the process by which organisms grow and develop. Modern developmental biology studies the genetic control of cell growth, differentiation and "morphogenesis," which is the process that gives rise to tissues, organs and anatomy. Embryology is sometimes reserved to refer more specifically to the study of organisms between the one-cell stage (generally, the zygote) and the beginning of free living. Embryology was originally a more descriptive science until the 20th century. Embryology or developmental biology today now deals with the various steps necessary for the correct and complete formation of the body of a living organism. In the United Kingdom and other countries the term is sometimes reserved specifically to the study of human embryos.

The related field of evolutionary developmental biology was formed largely in the 1990s and is a synthesis of findings from molecular developmental biology and evolutionary biology which considers the diversity of organismal form in an evolutionary context.

Often used model organisms for developmental biology are the round worm Caenorhabditis elegans, the fruit fly Drosophila melanogaster, the zebrafish Brachydanio rerio, the mouse Mus musculus, and the weed Arabidopsis thaliana. The findings of developmental biology can help to understand developmental malfunctions such as chromosomal aberration, for example, Down syndrome. An understanding of the specialization of stem cells to specific tissues and organs could lead to the specific cloning of organs for medical purposes.

Contents

1 Molecular mechanisms of development 2 Developmental model organisms 3 See also 4 External links

Molecular mechanisms of development

During the second half of the 20th century the types of molecules involved in embryonic development were identified. Transcription factors are the key regulators of which genes are expressed in cells. Transcriptional control in the various differentiated cell types allows each type of cell (epithelial, muscle, neuron, etc) to express different amounts of the possible proteins. The transcription factors are regulated by signal transduction pathways that relay signals from outside of cells to the cell nucleus. Signal transduction pathways often involve receptors, receptor ligands and enzymes such as tampons. One key class of genes that are differentially regulated by transcription factors in different cell types are genes for cell adhesion proteins. Cell adhesion proteins are among the key regulators of morphogenesis.

Concepts in developmental biology

allantois, amnion, blastocyst, blastomere, blastula, blastulation, chorion, chrysalis, cleavage, ectoderm, embryo, embryogenesis, embryogeny, embryology, endoderm, extra-embryonic membrane, fetus (or foetus), gastrula, gastrulation, germ layer, germ plasm, germination, induction, juvenile, larva, maternal effect, mesoderm, metamorphosis, morphogenesis, morula, neoteny, neural development, nymph, ontogeny, oosperm, ovism, paedogenesis, pangenesis, phylogeny, primordium, pupa, rudiment, teratology, zygote

Developmental model organisms

Vertebrates

• frog
• zebrafish
• chick
• mouse (Mammalian embryogenesis)

Invertebrates

• sea urchin
• roundworm
• fruit fly (Drosophila embryogenesis)

Plants (Plant embryogenesis)

• Arabidopsis
• Maize
• Snapdragon

See also

• Important publications in developmental biology
• morphogenesis, embryogenesis

External links

• Developmental Biology (http://www.ncbi.nlm.nih.gov:80/books/bv.fcgi?call=bv.View..ShowTOC&rid=dbio.TOC&depth=2) by Scott Gilbert. (online textbook)
• Virtual Library - Developmental Biology (http://www.sdbonline.org/Other/VL_DB.html)

de:Entwicklungsbiologie eo:Embriologio es:Embriología et:Embrüoloogia fr:Biologie du développement it:Embriologia ja:発生生物学 hu:Fejlődéstan nl:Ontwikkelingsbiologie simple:Developmental biology sl:razvojna biologija sl:Embriologija zh:胚胎学