Table 1. Summary of fertility and cytogenetic data in mTert^+/+, mTert^+/—, and mTert^—/— mice.

Generation	Average total offspring* (no. of mating pairs)	Testes mean ± SD,† mg	% SFE‡ (no. of mice)	End-to-end fusions per metaphase§ (no. of metaphases)	% Aneuploidy¶
B6 wt	26 (7)	174 ± 22 (7)	0.08 (4)	0 (47)	14.9
B6 BC8+/—	27 (2)	178 ± 34 (3)	0.21 (3)	0.03 (37)	ND
B6 G1	22 (10)	ND	ND	ND	ND
B6 G2	8 (6)	131 ± 52 (5)	0.7 (2)	0 (33)	ND
B6 G3	5 (11)	151 ± 57 (7)	4.0 (2)	0 (36)	39.0
B6 G4	4 (7)	97 ± 50 (6)	15.4 (2)	0 (42)	29.0
Mixed G6	9 (4)	140, 189 (2)	2.3 (2)	0.18 (33)	ND
Mixed G7	7 (6)	72 ± 10 (3)	5.5 (3)	0.09 (44)	15.9
Mixed G8	2 (9)	76 ± 76 (7)	10.7 (2)	0 (34)	53.0

B6, C57BL/6; mixed, C57BL/6/129; BC8+/—, mTert^+/— backcrossed for eight generations; ND, not determined.

^*Animals aged 8—20 weeks were mated, the total number of pups produced during a 6-month period was recorded for each mating pair, and the average total number of pups for each generation was calculated

^†Expressed in milligrams. Number of mice analyzed is indicated in parentheses. n = 7 (B6 wt), 3 (BC8+/—), 5 (B6 G2), 7 (B6 G3), 6 (B6 G4), 3 (mixed G7), and 7 (mixed G8). Only two mixed G6 males were examined for testicular mass, therefore both values are listed

^‡Expressed as percentage of all chromosome ends with no fluorescent signal. The number in parentheses is the number of mice measured per generation (400 chromosomes per mouse). Student's t tests revealed a statistically significant increase in SFE in B6 G3, B6 G4, mixed G7, and mixed G8 mice compared with wild-type control mice

^§Represents dicentric chromosomes only. Number in parentheses indicates the number of metaphases measured. Number of mice represented is the same as the % SFE column

^¶Represents metaphases with greater or less than 40 chromosomes. Numbers of metaphases measured and mice represented is same as in the %SFE column