 In fertilization and breeding experiments ( and especially when discussing Mendel 's laws ) the parents are referred to as the " P " generation and the offspring as the " F1 " ( first filial ) generation . When the F1 offspring mate with each other , the offspring are called the " F2 " ( second filial ) generation . One of the common diagrams used to predict the result of cross @-@ breeding is the Punnett square . 
