Question

Which step is NOT a part of the SOS repair?

A. LexA repressor binds to the SOS boxes in repair genes promoters and represses their activity under normal conditions

B. RecA cuts LexA thus inhibiting the inhibitors activity

C. Repair uvrB gene is regulated by dual promoter, one constitutive and one inducible

D. UV exposure activates RecA

Answer 1

The incorrect step in the SOS repair process is 'C. Repair uvrB gene is regulated by dual promoter, one constitutive and one inducible.' SOS repair begins with the repression by LexA and is activated by DNA damage and RecA.

Step-by-step explanation:

The step that is NOT a part of the SOS repair process is C. Repair uvrB gene is regulated by dual promoter, one constitutive and one inducible.

The SOS repair response is a bacterial mechanism of DNA repair that is induced by DNA damage. Here's how it works: under normal conditions, the LexA repressor binds to the SOS boxes in repair genes promoters and represses their activity.

Upon DNA damage, such as UV exposure, RecA is activated and assists in the autodigestion of LexA, thus relieving the repression and allowing DNA repair genes to be expressed.

This information is crucial for understanding the mechanism by which cells respond to DNA damage, which has implications for antibiotic resistance, cancer, and the treatment of genetic disorders.

correct answer C. Repair uvrB gene is regulated by dual promoter, one constitutive and one inducible

Answer 2

The step not part of the SOS repair is C, which suggests the uvrB gene is regulated by dual promoters; in the context of SOS repair, uvrB is not mentioned to be controlled in this manner.

Step-by-step explanation:

Understanding SOS Repair Mechanisms

The question seems to focus on the SOS repair system, a bacterial DNA repair mechanism activated upon extensive DNA damage, such as UV irradiation.

Within the SOS response, several DNA repair genes are upregulated, and this upregulation is tightly regulated by the LexA repressor and the RecA protein.

Initially, LexA binds the SOS boxes in repair genes' promoters, keeping them silent under non-stressful conditions.

Upon DNA damage, RecA is activated and promotes LexA repressor autocleavage, lifting the repression and allowing transcription of repair genes.

Option C is incorrect for the SOS repair context as it suggests that the repair gene uvrB is regulated by two promoters, one constitutive and one inducible.

However, this dual promoter system is not a part of the canonical SOS repair response.

It is important to note that RecA has homologs in other organisms such as Rad51 in eukaryotes, suggesting a conserved mechanism for DNA repair across evolution.

RecA plays a pivotal role in recognizing DNA damage and initiating repair processes, including homologous recombination, which is important for accurately repairing DNA breaks.