A dihybrid is an organism that is heterozygous at two different genetic loci. It results from a cross between parents with different traits for both of these loci.
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A dihybrid cross involves individuals that are heterozygous for two traits, such as AaBb.
The phenotypic ratio typically observed in the offspring of a dihybrid cross is 9:3:3:1.
Mendel's law of independent assortment states that alleles for different traits are distributed to sex cells (& offspring) independently of one another.
In a Punnett square for a dihybrid cross, there are 16 possible genotype combinations.
Mendel used dihybrid crosses to demonstrate the independent assortment of genes.
Review Questions
What phenotypic ratio is expected in the offspring of a dihybrid cross?
How does Mendel's law of independent assortment apply to dihybrid crosses?
How many boxes are found in the Punnett square of a typical dihybrid cross?
Related terms
Monohybrid Cross: A genetic mix between two individuals who have homozygous genotypes which result in opposite phenotypes for a certain genetic trait.
Independent Assortment: The principle stating that genes located on different chromosomes are inherited independently from one another.
Punnett Square: A diagram that is used to predict the genotypes and phenotypes of offspring from a particular genetic cross or breeding experiment.