Chapter 8.3: Alleles, Genes, and the Environment Interact to Produce Phenotype

Flashcards from Chapter 8.3 of Principles of Life, 3rd Edition.

Dominance hierarchy

This occurs with multiple alleles affecting the same gene, with certain alleles dominating others in expression

• The specific two the individual has affects the phenotype in different ways

• Seen in rabbit coat colors, ranging from dark gray to albino

Incomplete dominance

A state where a heterozygote shows a phenotype intermediate between the dominant and recessive versions

• Seen in eggplants exhibiting purple, violet, and white phenotypes

Codominance

A state where two alleles of a gene produce both of their phenotypes in a heterozygote

• Seen with A, B, AB, and O blood typing with I^A, I^B, and i alleles

Pleiotropic gene

A gene that affects multiple characters

• Seen with cystic fibrosis, which causes several bodily disorders

Epistasis

When one gene affects the expression of another gene

• Seen with labrador coat color being dependent on both pigment production and injection functions

Discrete traits

Traits that are easily distinguished from one another with few categories

• Typically have one or a few Mendelian genes that determine variation

Quantitative traits

Traits that vary within a range, affected by many genes at varying levels

• Includes height, weight, and more

Phenotypic plasticity

When a genotype is expressed differently across environments to create different phenotypes

• Seen with hydrangea color differing with soil acidity, or diet affecting height in adulthood

• Affects natural selection as differences are not genetic