The Genetic Basis of Complex Traits

Flashcards on The Genetic Basis of Complex Traits

Multifactorial traits

Traits determined by multiple genetic and environmental factors acting together; also referred to as complex traits or quantitative traits.

Genetic architecture of a complex trait

Specific effects and combined interactions of all genetic and environmental factors of a complex trait.

Continuous traits

Traits with a continuous gradation from one phenotype to the next, like height.

Categorical traits

Traits where the phenotype is determined by counting, such as the number of hens’ eggs laid.

Threshold traits

Traits with only two or a few phenotypic classes, but their inheritance is determined by multiple genes and the environment, such as adult-onset diabetes.

Mean

The average of all phenotypic values.

Variance

The spread of distribution estimated by squared deviation from the mean.

Standard deviation

Square root of the variance.

Small standard deviation

Suggests that most data are very close to the mean, resulting in a narrow curve.

Large standard deviation

Suggests a broad distribution of data, resulting in a broad curve.

Genotypic variance

Variation in phenotype caused by differences in genotype.

Environmental variance

Variation in phenotype caused by the environment.

Total variance

Combined effects of genotypic and environmental variance.

Environmental variation

All phenotypic variation within a single population of an inbred line.

Genotype-environment (G-E) interaction

Environmental effects on phenotype differ according to genotype.

Genotype-by-sex interaction

Same genotype produces different phenotype in males and females.

Broad-sense heritability (H2)

The proportion of phenotypic variation in a population due to all genetic effects combined.

Narrow-sense heritability (h2)

The proportion of phenotypic variation in a population due to additive effects of individual alleles.

M* – M

Selection differential (S)

M' – M

Response to selection (R)

Correlated response

Effect of selection for one trait on a non-selected trait.

Quantitative Trait Loci (QTLs)

Genes that affect a quantitative trait.

Localized by

Determining associations between phenotype and alleles of polymorphic DNA markers.

Look for

Statistical correlations between presence of SNP alleles and the phenotype in question.