Practice question

MutH is methylation-sensitive endonuclease whose nicking activity is licensed by MutS-MutL complex bound at mismatch. Parental strands carry N6-methyladenine at GATC sites due to Dam methylase, whereas newly synthesized strands remain unmethylated for several minutes post-replication. MutH senses this chemical asymmetry and introduces single-strand break 5' to GATC on unmethylated strand. This incision creates entry point for helicase II UvrD and single-strand exonucleases ExoI, ExoVII, RecJ. Selective cleavage ensures degradation targets error-containing nascent strand while methylated template preserved for accurate resynthesis.