A painting probe for chromosome 14 was hybridized to metaphase cells from either a wild-type mouse spleen or non-malignant Atm^−/− mouse spleen. Structural abnormalities include translocations and large duplications or deletions visible by fluorescence in situ hybridization analysis.

Metaphases from 2 Atm^−/− spleens were pooled.

Metaphases from one wild-type (Atm^+/+) spleen.

Spleen cells were cultured separately with either concanavilin A or LPS (see “Materials and methods”) to stimulate T or B cells, respectively.