After the F_1 backcrossed white egg, orange egg and red egg strain, the RF_1 eggs produced black egg and white egg, black egg and orange egg, black egg and red egg, separately, in the ratio of 1: 1.

• F_1回交白卵,RF_1,分离黑卵,橙色卵成1:1,回交红卵则分离黑卵、红卵成1:1。