Punnett Squares

Punnett Square

A chart used to determine the probability of different genotypes and phenotypes appearing in offspring.

Genotypic Ratio

The ratio of different genotypes that can occur in offspring.

Phenotypic Ratio

The ratio of different phenotypes that can occur in offspring based on dominant and recessive traits.

Monohybrid Cross

Involves one gene with two alleles.

Dihybrid Cross

Involves two genes, each with two alleles.

Mendelian Genetics

The principles of heredity first formulated by Gregor Mendel based on his work with pea plants.

Alleles

Different forms of a gene that may exist at a specific locus.

Gametes

Reproductive cells (sperm and eggs) that carry alleles.

Dominant Trait

A trait expressed in an organism's phenotype, masking the effects of the recessive trait.

Recessive Trait

A trait that is masked by the dominant trait and is only expressed in the phenotype when two recessive alleles are present.

F2 Generation

The second filial generation, which is the offspring of the F1 generation.

Example of Monohybrid Cross

Ss × ss where S = long stems and s = short stems.

Dihybrid Cross Example

AaBb × AaBb with gametes AB, Ab, aB, ab.

Phenotypic Ratio of Dihybrid Cross

In a dihybrid cross, the phenotypic ratio is typically 9:3:3:1.

Inheritance Patterns

The genetic principles determining how traits are passed from parents to offspring.