The likelihood that a particular
DNA segment will be attacked by the
endonuclease enzyme DNase I, which breaks down DNA into smaller fragments by cleaving its
phosphodiester bonds. DNA segments which contain active genes that are regularly
transcribed are more prone to being cut apart by DNase I than inactivated genes, because the inactivated genes are generally within condensed regions of the
chromosome, while the active genes are in more open configurations for easy access for
transcription.
From the BioTech Dictionary at http://biotech.icmb.utexas.edu/. For further information see the BioTech homenode.