千里麦浪铺锦绣,万倾碧波奏华章。
看图,选择合适的问句,把序号填在括号里。
A. Does she like cows? B. What do you like?
C. Do the boys know snakes? D. Does he like sheep?
红眼(R)雌果蝇和白眼(r)雄果蝇交配,F1代全是红眼,自交所得的F2代中红眼雌果蝇121头,红眼雄果蝇60头,白眼雌果蝇0头,白眼雄果蝇59头,则F2代卵细胞中具有R和r及精子中具有R和r的比例为( )