<P> Some believe dedifferentiation is an aberration of the normal development cycle that results in cancer, whereas others believe it to be a natural part of the immune response lost by humans at some point as a result of evolution . </P> <P> A small molecule dubbed reversine, a purine analog, has been discovered that has proven to induce dedifferentiation in myotubes . These dedifferentiated cells could then redifferentiate into osteoblasts and adipocytes . </P> <P> Each specialized cell type in an organism expresses a subset of all the genes that constitute the genome of that species . Each cell type is defined by its particular pattern of regulated gene expression . Cell differentiation is thus a transition of a cell from one cell type to another and it involves a switch from one pattern of gene expression to another . Cellular differentiation during development can be understood as the result of a gene regulatory network . A regulatory gene and its cis - regulatory modules are nodes in a gene regulatory network; they receive input and create output elsewhere in the network . The systems biology approach to developmental biology emphasizes the importance of investigating how developmental mechanisms interact to produce predictable patterns (morphogenesis). (However, an alternative view has been proposed recently . Based on stochastic gene expression, cellular differentiation is the result of a Darwinian selective process occurring among cells . In this frame, protein and gene networks are the result of cellular processes and not their cause . See: Cellular Darwinism) </P> <P> A few evolutionarily conserved types of molecular processes are often involved in the cellular mechanisms that control these switches . The major types of molecular processes that control cellular differentiation involve cell signaling . Many of the signal molecules that convey information from cell to cell during the control of cellular differentiation are called growth factors . Although the details of specific signal transduction pathways vary, these pathways often share the following general steps . A ligand produced by one cell binds to a receptor in the extracellular region of another cell, inducing a conformational change in the receptor . The shape of the cytoplasmic domain of the receptor changes, and the receptor acquires enzymatic activity . The receptor then catalyzes reactions that phosphorylate other proteins, activating them . A cascade of phosphorylation reactions eventually activates a dormant transcription factor or cytoskeletal protein, thus contributing to the differentiation process in the target cell . Cells and tissues can vary in competence, their ability to respond to external signals . </P>

What causes cells with the same dna to differentiate
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