A dihybrid cross shows the simultaneous inheritance of two genes controlling separate characteristics.

Linked genes are located on the same chromosome and tend to be inherited together unless crossing over occurs.

Alleles for different genes segregate independently during gamete formation in meiosis.

The genotype is written by placing the alleles for one gene immediately followed by the alleles for the second gene.

It is important to keep the order consistent, always putting the same gene first to avoid confusion.

A true or pure breeding organism is homozygous for the traits being studied, consistently producing the same trait in offspring.

All F₁ offspring will have a heterozygous genotype, displaying both dominant traits in their phenotype.

For instance, if the parents had the genotypes GGYY and ggyy, the offspring would all have the genotype GgYy. F₁ offspring are always produced from one parent that is homozygous recessive and another that is homozygous dominant.

The actual offspring ratio may differ from the expected offspring ratio in a dihybrid cross due to random fertilisation of gametes or if the genes are linked.

A heterozygous dihybrid organism can produce four types of gamete.

For instance, if their genotype was GgYy, they could produce the following gametes:

GY, gY, Gy, and gy.

The expected ratio for this scenario is 9:3:3:1.

For instance, if the dominant traits were round and yellow seeds and the recessive traits were wrinkled and green seeds, the expected phenotype ratio would be: 

9 yellow and round : 3 yellow and wrinkled : 3 green and round : 1 green and wrinkled.