Chapter 12.3.1 (Exam 3) Epistasis Flashcards
Genes Can Interact to Produce a Phenotype
What is epistasis?
Phenotypic expression of one gene is influenced by another gene
What is one example of epistasis?
Coat color in Labrador retrievers:
Alleles for black and brown aren’t expressed unless allele E (for pigment deposition) is expressed
An ee dog is yellow regardless of which B alleles are present
Product of E is epistatic to product of B
What is inbreeding? What does it result in?
Mating among close relatives; can result in offspring with reduced fitness (inbreeding depression)
Why does inbreeding depression occur?
Close relatives tend to have the same deleterious recessive alleles
Inbreeding can produce offspring of smaller size and/or lower quality than matings between unrelated individuals
What is heterosis (hybrid vigor)?
Crosses between genetically different parent lines can result in offspring with superior qualities
What is one example of heterosis (hybrid vigor)?
Hybridized corn and other crops and animals have led to increased food production
The environment (e.g. light, temperature, nutrition, etc.) also affects the phenotype. What are some examples of this?
Point restriction coat patterns in Siamese cats and rabbits are caused by inactivity of the enzyme that produces dark fur at higher temperatures
What are the two parameters that describe the effects of genes and environment on phenotype?
Penetrance
Expressivity
What is penetrance?
Proportion of individuals with a certain genotype that show the phenotype
What is expressivity?
Degree to which genotype is expressed in an individual
What is quantitative variation? What is an example?
Phenotypes vary continuously over a range, e.g., height of individuals.
What is quantitative variation dependent on?
Quantitative variation is usually due to both genetic and environmental factors
