When solving genetics problems, it pays to know what patterns to look for. The parent genotypes and offspring phenotypic ratios in this table can help you figure out what kind of inheritance is at work.

Parent Genotypes Offspring Phenotypic Ratio Type of Inheritance
Aa x Aa 3 A_ : 1 aa Simple dominance, monohybrid cross
Aa x Aa 1 AA : 2 Aa : 1 aa Incomplete dominance
AaBb x AaBb 9 A_B_ : 3 A_bb : 3 aaB_ : 1 aabb Dihybrid cross
AaBb x AaBb 9 A_B_ : 3 A_bb : 4 aaB_ : aabb Recessive epistasis
AaBb x AaBb 12 A_B_ : A_bb : 3 aaBb : 1 aabb Dominant epistasis