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A conditional Knock-Out allows the deletion of a gene in a tissue -and/or time- specific manner. 
If the recombinase is expressed in the fertilized embryo, the generated model will be a full Knock-Out. 
If the recombinase is expressed only in a population of cells, the generated model will be a "tissue-specific" Knock-Out.

  • 1. Site-specific recombination sites are introduced into intronic sequences surrounding key exons.

  • 2. The resulting sequence corresponds to the conditional allele.

  • 3. This allele is designed so that a wild type transcript is produced.

  • 4. After recombination with a recombinase, the allele is deleted resulting in a Knock-Out.

ICS expertise:

  • Large ES resource already available (EUCOMMKOMP;NorCOMM). As a member of the EUCOMM consortium, the ICS has a strong experience using the EUCOMM and KOMP resources.
  • Our know-how in designing these models will reduce the risk that the conditional allele does not behave as the endogenous wild type allele.
  • This strategy is specially adapted for indispensable genes and for the study of the function of a gene in a specific biological system, organ or cell population. We recommend also this strategy for gene with unknown function(s).


  • Higher risk of production of truncated / partially functional protein after deletion of the conditional allele than a constitutive Knock-Out approach.
  • The size of the inter-LoxP fragment is limited; it can sorely exceed 3 kb as homologous recombination can occur between the two loxP sites.

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