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Fig. 6 | Genome Biology

Fig. 6

From: DNA polymerase stalling at structured DNA constrains the expansion of short tandem repeats

Fig. 6

A model for the regulation of the length of structured STRs. After initiation of DNA synthesis (a), if the DNA polymerase dissociates within an STR (b), its repetitive nature may induce an out-of-register realignment (c) of the newly synthesised DNA on the template strand, leading to the expansion of the repeat according to a strand slippage mechanism. After several rounds of expansion, the STR may reach a threshold length at which the repeat will accommodate thermodynamically stable structures that would trigger polymerase stalling (d) and induce error-prone DNA synthesis (e). Base substitution at the boundary of the structured STRs then dilutes the repetitive sequences within the flanks of the STR locus. The length of the structured repeats at equilibrium therefore results from the balance of two processes: strand slippage and error-prone DNA synthesis regulated by polymerase stalling at DNA structures

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