Figure 16-19. The SOS system.

Figure 16-19

The SOS system. DNA polymerase III, shown in blue, stops at a noncoding lesion, such as the TC photodimer shown here, generating single-stranded regions that attract the Ssb protein (dark purple) and RecA (light purple), which forms filaments. The presence of RecA filaments helps to signal the cell to synthesize UmuD (red circles), which is cleaved by RecA to yield UmuD′ (pink circles) and UmuC (yellow ovals). The UmuC is recruited to form a complex with UmuD′ that permits DNA polymerization to proceed past the blocking lesion.

From: Induced mutations

Cover of An Introduction to Genetic Analysis
An Introduction to Genetic Analysis. 7th edition.
Griffiths AJF, Miller JH, Suzuki DT, et al.
New York: W. H. Freeman; 2000.
Copyright © 2000, W. H. Freeman and Company.

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