Table 1. Chromosome damage scored following exposure of a 72-h blood culture to 1 Gy ¹³⁷Cs γ-rays 4 h before harvest.

Patient	No. of mitoses analysed	No. of tg	No. of tb	No. of trirad	No. of quad
A-T213 sample 1	50	21	1	0	1
A-T213 sample 2	50	25	4	0	0
A-T1	50	118	38	5	4
A-T2	50	74	20	1	2
Control	50	8	0	0	0

Abbreviations: tg=chromatid gaps; tb=chromatid breaks; trirad=triradial chromosomes; quad=quadriradial chromosomes.

A-T1 and A-T2 are classical ataxia telangiectasia (A-T) patients.