DNA/RNA Synthesis

RNA synthesis, which is also called DNA transcription, is a highly selective process. Transcription by RNA polymerase II extends beyond RNA synthesis, towards a more active role in mRNA maturation, surveillance and export to the cytoplasm. Single-strand breaks are repaired by DNA ligase using the complementary strand of the double helix as a template, with DNA ligase creating the final phosphodiester bond to fully repair the DNA.DNA ligases discriminate against substrates containing RNA strands or mismatched base pairs at positions near the ends of the nickedDNA. Bleomycin (BLM) exerts its genotoxicity by generating free radicals, whichattack C-4′ in the deoxyribose backbone of DNA, leading to opening of the ribose ring and strand breakage; it is an S-independentradiomimetic agent that causes double-strand breaks in DNA.