Epistatic interactions and testes abnormalities. (A) Epistatic interactions between regions. Bidirectional red arrows indicate positive epistatic interaction between regions I and IV and interaction of region I with (III.V). Bidirectional blue arrow indicates negative interaction between regions III and V. (B) TGCTs in congenic 3 mice. Specimens from left to right are: normal (N) pair of testes; tumor (T) in left testis and normal (N) right testis; normal left and tumor in right-testis; bilateral tumors in testes. (C) Abnormal testes from congenic 5 mice. Abnormal or small left testes (S) and normal (N) right testis. (D) Histological section of a small testis and (E) contralateral normal testis from congenic 5 mouse. In the small testes, spermatogenesis is arrested at specific stages. Few elongated spermatids are seen in the tubules.