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  1. represser.
  2. Genetics. a protein that binds DNA at an operator site and thereby prevents transcription of one or more adjacent genes.

Origin of repressor

From Latin, dating back to 1955–60; see origin at repress, -tor


or re·pres·sor

  1. a person or thing that represses.

Origin of represser

late Middle English word dating back to 1400–50; see origin at repress, -er1
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for repressor

Historical Examples

  • In his principal work, the "Repressor of over much blaming of the Clergy," ed.

    A Literary History of the English People

    Jean Jules Jusserand

British Dictionary definitions for repressor


  1. biochem a protein synthesized under the control of a repressor gene, which has the capacity to bind to the operator gene and thereby shut off the expression of the structural genes of an operon
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

repressor in Medicine


  1. One that represses.
  2. A protein, especially either of two proteins produced by regulatory genes, that blocks transcription of an operon.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

repressor in Science


  1. A protein that binds to an operator, blocking transcription of an operon and the enzymes for which the operon codes.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.