lec 6-Genetics and Molecular Biology: Gene Interaction II

Vocabulary-style flashcards covering gene interactions, epistatic phenotypic ratios, and the complementation test based on the lecture transcript.

Epistasis

A phenomenon where genes interacting with each other contribute to the same phenotype, modifying Mendelian ratios because one gene masks or alters the expression of another.

Complementary gene action

A type of epistasis where genes act in tandem to produce a phenotype; a homozygous recessive genotype at either locus produces the same mutant phenotype, typically resulting in a $9:7$ ratio.

Recessive epistasis

Occurs when the recessive genotype at one locus masks the effect of the genotype at a second locus, characteristic of the $9:3:4$ phenotypic ratio.

Dominant epistasis

A gene interaction where a dominant allele at one locus masks the effect of the genotype at another locus, typically resulting in a $12:3:1$ phenotypic ratio.

Duplicate gene action

Occurs when two different genes perform the same (redundant) function, leadind to a $15:1$ ratio because only the double homozygous recessive genotype produces a different phenotype.

Complementation test

A genetic test used to determine if two recessive mutations represent alleles of the same gene or are located in different genes.

Complementation group

A group of mutations that fail to complement each other; the total number of these groups equals the number of genes mutated that control a specific characteristic.

Anthocyanin

The purple pigment in peas produced by the interaction of dominant alleles at the C and P loci; its absence results in white flowers.

Agouti

A grayish mouse coat color formed by alternating bands of pigment, requiring dominant alleles at both the A and B loci ($A-B-$).

Complementation

The regeneration of the wild-type phenotype when two different recessive mutations are crossed, indicating the mutations are located in different genes.

$9:7$ Ratio

A phenotypic ratio indicative of complementary gene action, appearing when two independent dominant alleles must be present together to produce a specific phenotype.

$9:3:4$ Ratio

A modified dihybrid ratio always indicative of a recessive epistasis relationship between two genes.

$12:3:1$ Ratio

An F2 phenotypic ratio indicative of dominant epistasis, where a dominant allele of one gene masks the effect of the second gene locus.

$15:1$ Ratio

A phenotypic ratio in the F2 generation that indicates duplicate gene action, where two genes are redundant.

Californian corn snakes

An example where genes affecting the same trait (color) operate independently, maintaining standard Mendelian ratios at the phenotypic level.