CH 17 Vocab DONE

Quantitative (Complex) Trait

a trait with continuous variation resulting from effects of many genes and environmental influences

Continuous Trait

can be any value between two extremes

Meristic Trait

measured in whole numbers, counts

Threshold Trait

can only be present or absent, are polygenic while qualitative traits are not

Mean

central value of trait in sample

Variance

quantifies how individual measurements differ from the mean

Heritability

the proportion of the phenotypic variance resulting from genetic differences

Phenotypic Variance

variation of the trait in the sample population

Additive Genetic Variance (V_A)

variation due to the sum of individual effects of alleles affecting the trait

Dominance Genetic Variance (V_D)

variation due to dominant alleles

Genic Interaction Variance (V_I)

variation due to epistatic interactions between genotypes at different loci

Heritability

proportion of phenotypic variance due to genetic differences

Broad-sense Heritability

the proportion of phenotypic variance in a population that is attributal to all genetic effects

Narrow-sense Heritability

the proportion of total phenotypic variance in a trait that is attributal solely to additive genetic variance (V_A)

h²

narrow-sense heritability; slope of regression between parent and offspring, using y = mx + b

mean parental on x-axis, mean offspring on y-axis

Natural Selection

the differential reproduction of individuals with different genotypes, allowing individuals with certain genotypes to reproduce more than others

Artificial Selection

humans promote the reproduction of individuals with traits perceived as desirable

Selection Differential (S)

the difference between the mean of the original population and the mean of the population selected

Response to Selection (R)

the change in the trait after one generation of selection

Realized Heritability

an estimate of narrow-sense heritability calculated by measuring R relative to S, when R and S are known values