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"Developmental genetics" redirects here. For the journal formerly known as Developmental Genetics, see Genesis (journal).
For the journal, see Developmental Biology (journal).
Views of a Foetus in the Womb

Views of a Fetus in the Womb, Leonardo da Vinci, ca. 1510-1512. The subject of prenatal development is a major subset of developmental biology.

Developmental biology 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, and even regeneration and aging,[1] more recently.

Perspectives Edit

The development of a new life is a spectacular process and represents a masterpiece of temporal and spatial control of gene expression. Developmental genetics studies the effect that genes have in a phenotype, given normal or abnormal epigenetic parameters. The findings of developmental biology can help to understand developmental abnormalities such as chromosomal aberrations that cause Down syndrome. An understanding of the specialization of cells during embryogenesis has provided information on how stem cells specialize into specific tissues and organs. This information has led, for example, to the cloning of specific organs for medical purposes.[2][3] Another biologically important process that occurs during development is apoptosis—programmed cell death or "suicide." Many developmental models are used to elucidate the physiology and molecular basis of this cellular process. Similarly, a deeper understanding of developmental biology can foster greater progress in the treatment of congenital disorders and diseases, e.g. studying human sex determination can lead to treatment for disorders such as congenital adrenal hyperplasia.

Developmental model organisms Edit

File:DEV035048A.jpg

Often used model organisms in developmental biology include the following:


Studied phenomena Edit

Cell differentiation Edit

Differentiation is the formation of cell types, from what is originally one cell – the zygote or spore. The formation of cell types such as nerve cells occurs with a number of intermediary, less differentiated cell types. A cell stays a certain cell type by maintaining a particular pattern of gene expression.[12] This depends on regulatory genes, e.g. for transcription factors and signaling proteins. These can take part in self-perpetuating circuits in the gene regulatory network, circuits that can involve several cells that communicate with each other.[13] External signals can alter gene expression by activating a receptor, which triggers a signaling cascade that affects transcription factors. For example, the withdrawal of growth factors from myoblasts causes them to stop dividing and instead differentiate into muscle cells.[14]

Embryonic development Edit

File:HumanEmbryogenesis.svg

Embryogenesis is the step in the life cycle after fertilisation – the development of the embryo, starting from the zygote (fertilised egg). Organisms can differ drastically in how the embryo develops, especially when they belong to different phyla. For example, embryonal development in placental mammals starts with cleavage of the zygote into eight uncommited cells, which then form a ball (morula). The outer cells become the trophectoderm or trophoblast, which will form in combination with maternal uterine endometrial tissue the placenta, needed for fetal nurturing via maternal blood, while inner cells become the inner cell mass that will form all fetal organs (the bridge between these two parts eventually forms the umbilical cord). In contrast, the fruit fly zygote first forms a sausage-shaped syncytium, which is still one cell but with many cell nuclei.[15]

Patterning is important for determining which cells develop into which organs. This is mediated by signaling between adjacent cells by proteins on their surfaces, and by gradients of signaling secreted molecules.[16] An example is retinoic acid, which forms a gradient in the head to tail direction in animals. Retinoic acid enters cells and activates Hox genes in a concentration-dependent manner – Hox genes differ in how much retinoic acid they require for activation and will thus show differential rostral expression boundaries, in a colinear fashion with their genomic order. As Hox genes code for transcription factors, this causes different activated combinations of both Hox and other genes in discrete anteroposterior transverse segments of the neural tube (neuromeres) and related patterns in surrounding tissues, such as branchial arches, lateral mesoderm, neural crest, skin and endoderm, in the head to tail direction.[17] This is important for e.g. the segmentation of the spine in vertebrates.[16]

Embryonic development does not always proceed correctly, and errors can result in birth defects or miscarriage. Often the reason is genetic (mutation or chromosome abnormality), but there can be environmental influence (like teratogens) or stochastic events.[18][19] Abnormal development caused by mutation is also of evolutionary interest as it provides a mechanism for changes in body plan (see evolutionary developmental biology).[20]

Growth Edit

Growth is the enlargement of a tissue or organism. Growth continues after the embryonal stage, and occurs through cell proliferation, enlargement of cells or accumulation of extracellular material. In plants, growth results in an adult organism that is strikingly different from the embryo. The proliferating cells tend to be distinct from differentiated cells (see stem cell and progenitor cell). In some tissues proliferating cells are restricted to specialised areas, such as the growth plates of bones.[21] But some stem cells migrate to where they are needed, such as mesenchymal stem cells which can migrate from the bone marrow to form e.g. muscle, bone or adipose tissue.[22] The size of an organ frequently determines its growth, as in the case of the liver which grows back to its previous size if a part is removed. Growth factors, such as fibroblast growth factors in the animal embryo and growth hormone in juvenile mammals, also control the extent of growth.[21]

Metamorphosis Edit

Most animals have a larval stage, with a body plan different from that of the adult organism. The larva abruptly develops into an adult in a process called metamorphosis. For example, caterpillars (butterfly larvae) are specialized for feeding whereas adult butterflies (imagos) are specialised for flight and reproduction. When the caterpillar has grown enough, it turns into an immobile pupa. Here, the imago develops from imaginal discs found inside the larva.[23]

Regeneration Edit

Regeneration is the reactivation of development so that a missing body part grows back. This phenomenon has been studied particularly in salamanders, where the adults can reconstruct a whole limb after it has been amputated.[24] Researchers hope to one day be able to induce regeneration in humans (see regenerative medicine).[25] There is little spontaneous regeneration in adult humans, although the liver is a notable exception. Like for salamanders, the regeneration of the liver involves dedifferentiation of some cells to a more embryonal state.[24]

Developmental systems biology Edit

Computer simulation of multicellular development is a research methodology to understand the function of the very complex processes involved in the development of organisms. This includes simulation of cell signaling, multicell interactions and regulatory genomic networks in development of multicellular structures and processes (see French flag model or Category:Developmental biology journals for literature). Minimal genomes for minimal multicellular organisms may pave the way to understand such complex processes in vivo.

See also Edit

References Edit

  1. Wolpert L, Beddington R, Jessell T, Lawrence P, Meyerowitz E, Smith J (1998). Principles of development, 1st, Oxford university press.
  2. Anthony Atala, S. Bauer, S. Soker, J. Yoo, A. Retik (2006-04-04). Tissue-engineered autologous bladders for patients needing cystoplasty. The Lancet 367 (9518): 1241–1246.
  3. Wake Forest University (2006-04-03). Wake Forest Physician Reports First Human Recipients of Laboratory-Grown Organs. Press release. Retrieved on 2010-04-06.
  4. DOI:10.1242/dev.035048
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  5. (1996). Large scale genetics in a small vertebrate, the zebrafish. Int. J. Dev. Biol. 40 (1): 221–7.
  6. Wallingford, J., Liu, K., and Zheng, Y. 2010. Current Biology v. 20, p. R263-4
  7. Harland, R.M. and Grainger, R.M. 2011. Trends in Genetics v. 27, p 507-15
  8. Amaya E (2005). Xenomics. Genome Res. 15 (12): 1683–91.
  9. Keller G (2005). Embryonic stem cell differentiation: emergence of a new era in biology and medicine. Genes Dev. 19 (10): 1129–55.
  10. http://www.devbio.biology.gatech.edu/?page_id=2429
  11. http://www.devbio.biology.gatech.edu/?page_id=484
  12. Wolpert L, Beddington R, Jessell T, Lawrence P, Meyerowitz E, Smith J (2002). Principles of development, 2nd, 293–295, Oxford university press.
  13. (2007). Gene regulation: gene control network in development. Annu Rev Biophys Biomol Struct 36: 191.
  14. Wolpert L, Beddington R, Jessell T, Lawrence P, Meyerowitz E, Smith J (2002). Principles of development, 2nd, 304–307, Oxford university press.
  15. Wolpert L, Beddington R, Jessell T, Lawrence P, Meyerowitz E, Smith J (2002). Principles of development, 2nd, 41–50, 493, Oxford university press.
  16. 16.0 16.1 (January 1998). Segmentation of the vertebrate body. Anat. Embryol. 197 (1): 1–8.
  17. (July 1996). Retinoids and Hox genes. FASEB J. 10 (9): 969–78.
  18. (1986). Monitoring for congenital malformations. Annu Rev Public Health 7: 237–66.
  19. Wolf U (1997). Identical mutations and phenotypic variation. Hum Genet 100 (3–4): 305–21.
  20. (2008). Network Evolution of Body Plans. PLoS ONE 3 (7): e2772.
  21. 21.0 21.1 Wolpert L, Beddington R, Jessell T, Lawrence P, Meyerowitz E, Smith J (2002). Principles of development, 2nd, 467–482, Oxford university press.
  22. (November 2007). Concise review: mesenchymal stem cells: their phenotype, differentiation capacity, immunological features, and potential for homing. Stem Cells 25 (11): 2739–49.
  23. Gilbert SF (2003). Developmental biology, 7th, 575–585, Sinauer.
  24. 24.0 24.1 Gilbert SF (2003). Developmental biology, 7th, 592–601, Sinauer.
  25. Stocum DL (December 2002). Development. A tail of transdifferentiation. Science 298 (5600): 1901–3.

External links Edit

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Stages of Development in Developmental Biology
Early Embryonic Development
Fertilization - Egg activation - Clevage - Gastrulation - Regional specification
Late Embryonic Development
Endoderm Neurulation - Neural crest - Eye development - Cutaneous structure development
Mesoderm Heart development
Other Limb development - Germ line development - Programmed cell death - Stem cells
Post Embryonic Development
Metamorphosis - Regeneration - Aging

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Mammalian development of embryo and development and fetus (some dates are approximate - see Carnegie stages) - edit

Week 1: Zygote | Morula | Blastula/Blastomere/Blastosphere | Archenteron/Primitive streak | Blastopore | Allantois | Trophoblast (Cytotrophoblast | Syncytiotrophoblast | Gestational sac)

Week 2: Yolk sac | Vitelline duct | Bilaminar disc

Week 3: Hensen's node | Gastrula/Gastrulation | Trilaminar embryo Branchial arch (1st) | Branchial pouch | Meckel's cartilage | Somite/Somitomere | Germ layer (Ectoderm, Endoderm, Mesoderm, Chordamesoderm, Paraxial mesoderm, Intermediate mesoderm, Lateral plate mesoderm)

Histogenesis and Organogenesis

Circulatory system: Primitive atrium | Primitive ventricle | Bulbus cordis | Truncus arteriosus | Ostium primum | Foramen ovale | Ductus venosus | Ductus arteriosus | Aortic arches | Septum primum | Septum secundum | Cardinal veins

Nervous system: Neural development/Neurulation | Neurula | Neural folds | Neural groove | Neural tube | Neural crest | Neuromere (Rhombomere) | Notochord | Optic vesicles | Optic stalk | Optic cup

Digestive system: Foregut | Midgut | Hindgut | Proctodeum | Rathke's pouch | Septum transversum

Urinary/Reproductive system: Urogenital folds | Urethral groove | Urogenital sinus | Kidney development (Pronephros | Mesonephros | Ureteric bud | Metanephric blastema) | Fetal genital development (Wolffian duct | Müllerian duct | Gubernaculum | Labioscrotal folds)

Glands: Thyroglossal duct

Uterine support: Placenta | Umbilical cord (Umbilical artery, Umbilical vein, Wharton's jelly) | Amniotic sac (Amnion, Chorion)

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