Table 1.

Spontaneous mutation frequencies for Msh2^−/− thymic lymphomas (I), Msh2^−/− normal thymi (young mice) (II), Msh2^−/− normal thymi (older mice) (III), and Msh2^−/− normal brains from mice with thymic lymphomas (IV)

Tissue	Mice	Age, days	Sex	Total pfu*	No. of mutants	Mutation frequency, ×10−4	Mutation frequency, 100% clonality†
I. Thymic lymphoma	A	115	F	138,820	211	15.2	13.9
	B	121	F	234,760	759	32.3	24.2
	C	139	F	214,460	447	20.8	19.0
	D	132	F	207,740	581	28.0	25.6
	E	123	F	211,620	1729	81.7	44.9
	F	81	M	210,140	1105	52.6	32.4
	Mean					38 ± 23‡	27 ± 10
II. Normal thymus	G	19	F	295,020	166	5.6	2.6
	H	19	F	300,460	89	3.0	2.6
	I	26	M	281,640	155	5.5	4.0
	Mean					5 ± 1.2	3 ± 0.7
III. Normal thymus	J	132	F	185,100	109	5.9
	K	103	M	249,180	104	4.2
	Mean					5 ± 0.8
IV. Normal brain	E	123	F	220,080	89	4.0
	F	81	M	215,300	95	4.4
	Mean					4 ± 0.2

^*pfu = plaque-forming units. 

^†See Table 2. for clonality. 

^‡Mean ± SD.