Multiple choice The ratio 1 : 1 : 1 : 1 is obtained from a cross between the parents RRYY x rryy RRYY x rrYy RRYY x Rryy RrYy x rryy Reveal answer Fill a bubble to check yourself D Correct answer Explanation The cross RRYY x rryy cannot have the ratio 1 : 1 : 1 : 1.