Transcription Factors Regulate Gene Expression
While each body cell contains the organism's entire genome, different cells regulate gene expression with the use of various transcription factors. Transcription factors are proteins that affect the binding of RNA polymerase to a particular gene on the DNA molecule.
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"OpenStax College, Cellular Differentiation. December 11, 2013."
http://cnx.org/content/m46036/1.4/
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