Why is it important to couple transcription and re-pair? Unlike actively dividing E. coli and most other prokaryotes, most of the cells in a multicellular organism are terminally differentiated and no longer dividing, so replication repair is not possible. These cells are not dead, however; their genes are being actively transcribed into mRNAs, which are translated into proteins. DNA that is damaged in these cells must also be repaired, since mutations in certain genes could have devastating consequences to the health of the whole organism. As you will see in Chapter 17, most cancerous tumors de-velop from somatic cells that have sustained mutations that have not been repaired. POSTREPLICATION REPAIR Some repair pathways are capable of recognizing errors that usually occur during replication but fail to be corrected by the 3 9-to-5 9 proof-reading function of the replicative polymerase. One such pathway, termed the mismatch-repair system, can detect such mismatches. Mismatch-repair systems have to do at least three things: 1. Recognize mismatched base pairs 2. Determine which base in the mismatch is the
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This note was uploaded on 01/10/2011 for the course BIOL BIOL taught by Professor Johnson during the Spring '08 term at Aberystwyth University.