Alternate-2 disjunction in the german cockroach.

The evidence in support of two types of alternate disjunction in translocation heterozygotes from the German cockroach, Blattella germanica (L.), is reviewed. When unique cytomorphological features occur in the translocation figure, the two types of alternate disjunction are identifiable regardless of the angle of observation. Photographs supporting this contention are presented for alternate-1 and alternate-2 disjunction in T(7;12)/7;12 . Other evidence in support of the existence of alternate-2 disjunction is also presented.