Uploaded April 2026 | Updated September 2026, 2 weeks ago
SOS, DNA repair is a mechanism by which the cell tries to fix the broken pieces of DNA. The main enzyme involved in SOS, DNA repair is DNA polymerase IV and DNA polymerase V. The function of these polymerase is to add nucleotides on the broken pieces of DNA. However these polymerase does not care about perfect paring of A with T and G with C. As a result it causes mutations because of mismatches. The genes for polymerase VI and polymerase V are repressed (switched off) by a repressor protein called LexA. When DNA gets damaged it results in formation of single stranded DNA. RecA protein binds the single stranded DNA and forms a nucleoprotein complex. When this complex interacts with LexA, the lexA carries out autocatalysis of itself. As LexA is now removed, The genes for DNA polymerase VI and V becomes free for transcription.
SOS, DNA repair is a mechanism by which the cell tries to fix the broken pieces of DNA. The main enzyme involved in SOS, DNA repair is DNA polymerase IV and DNA polymerase V. The function of these polymerase is to add nucleotides on the broken pieces of DNA. However these polymerase does not care about perfect paring of A with T and G with C. As a result it causes mutations because of mismatches. The genes for polymerase VI and polymerase V are repressed (switched off) by a repressor protein called LexA. When DNA gets damaged it results in formation of single stranded DNA. RecA protein binds the single stranded DNA and forms a nucleoprotein complex. When this complex interacts with LexA, the lexA carries out autocatalysis of itself. As LexA is now removed, The genes for DNA polymerase VI and V becomes free for transcription.
