FIG 9.

rDNA sequence variation in young and old C57BL/6 mice. rDNA sequences from three old (old 1 to old 3) and three young (young 1 to young 3) C57BL/6 mice were determined and compared to the reference sequence. The mutation rate at each nucleotide position was calculated as described in the legend to Fig. 7. (A to C) Mutations rates in old mice 1 to 3 were compared to the rate in young mouse 1 for the indicated genes. (D) Mutation rates in three young mice. (E) Average mutation rates. Noncoding regions are shown in gray. The mutation rate is based on differences from the reference sequence (as described in the legend to Fig. 8).