Morphogen

As morphogens signal molecules called that control the pattern formation ( morphogenesis ) during the development of multicellular organisms. Morphogens are in a tissue not evenly distributed, but in different concentrations. They are formed at a localized source and then diffuse into the surrounding tissue. They form concentration gradients that mediate the neighboring cells in the tissue indirectly spatial position information. Because only when certain thresholds are reached in the concentration of morphogen be in the target cell, the necessary genes that control the development, enabled. Cells can thus no longer only answer pure yes / no responses, but it can be a function of the concentration gradual reactions allows: A high concentration of the morphogen can enable example, a group of genes, an average concentration will activate a different group and a low concentration activates a third group of genes. This system is also called a French flag model. This range is sometimes referred to as the morphogenetic field.

A morphogen so influenced an entire set of cells and forces them different reactions, depending on how far they are away from the source of production of the morphogen.

Some of the best studied morphogens Bicoid and Hunchback are the proteins that play an important role in early embryogenesis of Drosophila melanogaster. These are transcription factors that can activate other genes. Other morphogens are growth factors, such as proteins, Hedgehog, Wingless and Decapentaplegic.