TABLE 2.

Mutation counts in WT, rExoN1, and rExoN3 mutant viruses

Virus and clone	No. of mutationsa
	Region a	Region b	Region c	Mean per 10,000 ntb
VUSS3p5 (WT)
c1	0	0	0
c2	0	1	0
c3	0	0	0	0.29
c4	1	0	0
c5	0	1	0
c6	0	1	0}
rExoN1p5
c1	2	2	3
c2	1	6	4
rExoN3p5				4.4
c1	3	4	4
c2	2	2	2}

^aRegions a to c refer to the sequenced regions of the MHV genome shown in Fig. 5. A total of 120,978 nt were sequenced for WT, and 80,652 nt were sequenced for the combined mutant viruses.

^bMean values for WT and the combined mutants were obtained by normalizing the mutation count in each region of each clone as mutations per 10,000 nt, summing the normalized values, and then dividing by the number of genome fragments sequenced (18 for WT and 12 for the combined mutants). A significant difference in the means was observed between WT and the combined rExoN1 and rExoN3 mutants (P < 0.001, Wilcoxon rank-sum test).