Inheritance of NORs by progeny of triploid females RRL (right) and RLL (left). The chromosome set represented by one copy is eliminated before oogenesis (marked by X) and the double one is segregated into eggs (represented by ovals). After fertilization (in this case by ridibundus sperm), two types of progeny arises: with two (A and C) and with one (B and D) NOR. The lack of NORs are transmitted either by lessonae (white) or by ridibundus (dark grey) chromosome sets. NORs are represented by black dots.