There are many repair systems that operate in adult cells that have stopped dividing. They are as follows:
1. NHEJ – Non-Homologous End Joining. In this method, the damage is first recognized and NHEJ pathway is initialized. Two proteins form a heterodimer that prevents further damage. Also, the recruitment of other proteins that trim the ends of strand is done by these proteins.
2. Direct reversal - This method is useful in reversing the damages in DNA chemically. This method is specific to type of damage. This is a most energy efficient method.
3. Excision repair - The mechanism involved in this method is able to recognize and remove damaged or inappropriate nucleotides. From the complementary strand of DNA, they are able to determine the correct sequence.
4. Transcription-coupled repair (TCR): It is a specialized nucleotide excision repair. In this method, lesions from the template DNA strands of actively transcribed genes are removed.