Unit 3 - Ch. 24: Quantitative Genetics Flashcards
What is quantitative genetics?
The study of traits that vary continuously and are influenced by multiple genes and environment
What is the difference between qualitative and quantitative traits?
• Qualitative: Discrete phenotypes (e.g., blood type)
• Quantitative: Continuous range of values (e.g., height, weight)
What does a frequency distribution graph show?
The range and frequency of phenotypes for a quantitative trait.
What does the mean (x̄) tell you in quantitative genetics?
The average trait value in a population
What does variance (s²) represent?
The spread or variability of trait values around the mean
What is covariance in quantitative traits?
It measures how two traits or a trait and an environmental factor vary together
Define heritability
The proportion of phenotypic variation due to genetics
What does it mean if heritability (H²) = 1?
All variation is genetic
What does it mean if heritability (H²) = 0?
All variation is due to the environment
What are the components of phenotypic variance (Vₚ)?
• Genetic variance (V_G)
• Environmental variance (V_E)
• Interaction variance (V_GxE)
• Association variance (V_G↔E)
What is polygenic inheritance? How do environmental factors affect it?
When multiple genes influence a single trait, producing continuous variation
They broaden the range of phenotypes, even for the same genotype
Why can’t Punnett squares be used for polygenic traits?
Because the number of genotypes is too large and phenotypes may overlap
What are Quantitative Trait Loci (QTL)?
Specific genomic regions associated with variation in a quantitative trait
What is phenotypic plasticity?
The ability of one genotype to produce different phenotypes in different environments
What is selective breeding? How is it used in agriculture?
Human-directed breeding to enhance desirable traits in animals and crops
To produce modern crops and livestock from wild ancestors (e.g., mustard into kale, broccoli)
