Chapter 5 : The inheritence of complex traits

Discontinuous variation

Phenotypes falling into distinct, nonoverlapping categories

Continuous variation

Phenotypes distributed in an overlapping fashion from one extreme to another

Monogenic traits

Traits controlled by a single gene

Complex traits

Traits controlled by multiple genes and environmental factors

Polygenic traits

Traits controlled by more than one gene

Multifactorial traits

Traits controlled by multiple genes and environmental influences

Polygenic inheritance

Inheritance pattern of traits controlled by multiple genes

Bell-shaped curve

Distribution of phenotypic variation in a population for a polygenic trait

Additive model

Model for analyzing polygenic traits assuming equal effects of each gene

F2 generation

Offspring generation resulting from the cross of two parental generations

Phenotypic classes

Different categories of phenotypes based on genetic variations

Gametes

Haploid cells involved in sexual reproduction, carrying genetic information

Polygenic Traits

Controlled by multiple genes, each contributing slightly to the phenotype

Regression to the Mean

Offspring tend to exhibit phenotypes closer to the population average

Multifactorial Traits

Influenced by multiple genes and environmental factors

Epigenetics

Reversible DNA or histone modifications altering gene expression

Genetic Liability Threshold

Point where genotypes above express affected phenotypes under specific conditions

Recurrence Risk

Risk of having another affected child based on factors like consanguinity and defect severity

Phenotypic Variation

Differences in phenotype due to genetic and environmental influences

Heritability

Expression of how much phenotype variation is due to genotype differences

Environmental Variance

Phenotypic differences due to environmental factors in a population

Correlation Coefficients

Measure genetic relatedness between individuals, used to calculate heritability

Twin Studies

Used to determine the influence of genetics and environment on traits

Identical Twins

Share genotype but have different environments

Adopted Children

Have different genotypes but share the same environment

Monozygotic Twins

Genetically identical twins from a single fertilization event

Dizygotic Twins

Twins from separate fertilizations sharing about 50% of genes

Obesity Heritability

Obesity has a strong genetic component, about 70%

Leptin

Weight-controlling hormone encoded by the ob gene

Leptin Receptor Gene

Gene (LEPR) encoding the receptor for leptin

Genome-wide Association Studies

Identify genes linked to obesity and other traits

Human Height Genetics

Height is controlled by over 50 genes with 80-90% heritability

Polygenic Trait

Trait influenced by multiple genes and environmental factors

IQ Heritability

Intelligence has a genetic component with a heritability of 0.6-0.8