<em>For a dihybrid cross in which the two genes concerned obey simple dominant/recessive law and are independently assorting, </em><em>four phenotypes are produced in the ratio 9:3:3:1. </em>
The dominant gene takes up the largest ratio (9/16) while the recessive gene takes up the smallest (1/16). Any deviation from 9:3:3:1 and the number of phenotypes produced from a dihybrid cross is an indication that the genes involved do not obey Mendelian laws.
The independent variable determines the value that needs to be calculated or the decision that needs to be made from the observations of the experiment. Hence, experimental design decision would most likely produce invalid and unreliable results when having more than one independent variable.
