Genetics: Dihybrid Cross, Epistasis, & Non-Mendelian Allele Interaction

Flashcards covering Dihybrid Crosses, Epistasis, Incomplete Dominance, and Codominance as per the lecture notes.

Dihybrid Cross

A genetic cross between individuals differing in two pairs of genes (or two characteristics).

Epistasis

The interaction of genes that are not alleles, where one gene masks or interferes with the expression of another, particularly if the interaction is antagonistic.

Yellow Lab (Coat Color Epistasis)

A dog with genotype 'ee' which results in no dark pigment in the fur, regardless of B/b alleles.

Chocolate Lab (Coat Color Epistasis)

A dog with genotype 'Ebb' where the 'E' allows dark pigment, but 'bb' causes brown fur.

Black Lab (Coat Color Epistasis)

A dog with genotype 'EB' where 'E' allows dark pigment, and 'B' results in black fur.

Trihybrid Cross Gene Combinations

A genetic cross involving three different traits, resulting in 2^3 = 8 possible gene combinations for gametes.

Genotypic Ratio (GR)

The ratio of different genotypes resulting from a genetic cross.

Phenotypic Ratio (PR)

The ratio of different phenotypes (observable traits) resulting from a genetic cross.

Law of Incomplete Dominance

A principle where a cross between homozygous dominant and recessive genes results in heterozygous progeny determining an intermediate trait, meaning both alleles exert an effect and jointly produce an intermediate phenotype.

Incomplete Dominance Example (Flower Color)

In flowers, a cross between a red flower (RR) and a white flower (rr) results in pink flowers (Rr).

Law of Codominance

A principle where a cross between homozygous dominant and recessive genes results in heterozygous progeny determining a phenotype where both the dominant trait and recessive trait are expressed simultaneously.

Codominance Example (Cattle Coat Color)

In cattle, a cross between red-haired (RR) and white-haired (rr) cattle results in roan cattle (Rr), which express both red and white hairs.

Cystic Fibrosis (Genetic Context)

An inherited condition demonstrating incomplete dominance, where heterozygotes (Ff) show an intermediate chloride concentration in sweat compared to homozygous normals (FF) and affected individuals (ff).