Previous experimental studies suggest that the mutation rate is nonuniform 
across the yeast genome. To characterize this variation across the genome more 
precisely, we measured the mutation rate of the URA3 gene integrated at 43 
different locations tiled across Chromosome VI. We show that mutation rate 
varies 6-fold across a single chromosome, that this variation is correlated with 
replication timing, and we propose a model to explain this variation that relies 
on the temporal separation of two processes for replicating past damaged DNA: 
error-free DNA damage tolerance and translesion synthesis. This model is 
supported by the observation that eliminating translesion synthesis decreases 
this variation.