TABLE 1.

Nucleotide sequences of viruses possessing M vRNAs derived from a pool of mutant M vRNA segments^a

Mstop	Nucleotide sequence at position 972-1007 (3′ to 5′)	No. of samplesb
	ACUCACUCAGUAAAACAGUUGUAUCUCGACCUCAUU
1	ACUCACUACCCUCUUUUUCCCGAUGUGCUUUUUAUU	1
2	ACUCACUACUAGAUUACUAACUAAAUUAAAGCUAUU	2
3	ACUCACUUUUACAAUUUUUUAUCACAAAUUUCACUU	1
4	ACUCACUUAACACUUUCAACCAUGACUAAGCUUAUU	4
5	ACUCACUCACUAACAUUAUAAUUACUCCAGACUAUU	2
6	ACUCACUCCUUAAUUACCAAAAAUGCAAUUUGUAUU	5
7	ACUCACUCAAUGGCUGCAAUACUUUUCAUCACCUUU	1
8	ACUCACUAUACAAAAUCCUUUCUCUGAUUAAGUAUU	1
9	ACUCACUACGCAUUAUAUCAUAUCAUCGUAAACAUU	2
10	ACUCACUUAAUACAUUAGAUCUUUUUCGAGUACAUU	1
11	ACUCACUACCUAUUAUUACAUAAUAUUUUGCAUAUU	2
12	ACUCACUAAUCCACAUCACUACAUUCCUCUUUCCUU	1
13	ACUCACUUCUUAAUCAUAAUAUUUACUAGUCAACAU	1
14	ACUCACUUAAUUUAUAUAUAUUUAAUAUCUAGUAUU	2
15	ACUCACUUUCACAAUAUUUUAUACACUCAAUACAUU	1
16	ACUCACUACCCAAUUUUCAUCUAUCUGUCUAGUGUU	1
17	ACUCACUCAAUUUAAAUUUAGGUUCCUUUUUGUCUU	1
18	ACUCACUCCGAUUUAAUCAAUUUCGAAUGCUAGAUU	1
19	ACUCACUAUUAUAUAUUAAACCCUCUACAGACUCUU	1
20	ACUCACUUAUAAACCUAAUUAAUCUACUAGAUUAUU	2
21	ACUCACUUUUACAGUAGCAUUUUUCCUCACACCAUU	1
22	ACUCACUAACUUUUAUGUACGUCAUUACAAAUUAUU	1
23	ACUCACUCCAAUCAAGACCUUUAAAACACACCACUU	1
24	ACUCACUGCAUCAAGACGUCAACACUAGUUAACAUU	1
25	ACUCACUACAUGAUUAGUAAUGAAAGAUUAUACCUU	1

^aReverse-transcription PCR products from mutant viruses were sequenced directly. Nucleotides identical to the wild-type are roman, stop codons are underlined, and the conserved uracils at the 5′ end (see text for details) are bold.

^bNumber of clones possessing the indicated sequence.