morphogen
morphogen A substance that determines the developmental fate of part of an embryo. During development, different morphogens are produced within the embryo or by cells of the surrounding maternal tissue. They diffuse through the embryonic tissue, each one establishing its own concentration gradient, and together they form a chemical pattern on which embryonic development is based (see pattern formation). The complex interplay of these morphogen gradients regulates the activity of genes in different regions of the embryo and ultimately brings about the differentiation of the tissues and organs appropriate to the different regions of the embryo, i.e. morphogenesis. In the development of the fruit fly Drosophila, for example, the anterior and posterior ends of the egg are ‘signposted’ by proteins encoded respectively by bicoid and nanos genes in maternal follicle cells. The messenger RNAs from these genes accumulate at opposite ends of the egg cell (oocyte), and their products subsequently diffuse into the fertilized egg, thereby establishing its polarity at the outset of development. These represent the beginning of a cascade of morphogens that influence gene activity in an increasingly precise manner.
morphogen
morphogen An environmental factor, such as a chemical substance, that establishes a concentration gradient affecting morphogenesis in organisms exposed to it.
morphogenesis
morphogenesis (mor-foh-jen-i-sis) n. the development of form and structure of the body and its parts.
morphogenesis
morphogenesis The development, through growth and differentiation, of form and structure in an organism.
morphogenesis
morphogenesis The development of the form and structure of an organism by growth and differentiation.
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Morphogenesis
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Morphogenesis