CH 5 PPT SU24_a686008b4a2827c73b343ebd89bb33b6

Discontinuous Variation

Phenotypes that fall into two or more distinct, nonoverlapping categories.

Continuous Variation

Phenotypes that are distributed from one extreme to another in a continuous, overlapping manner.

Complex Traits

Traits that are controlled by multiple factors rather than a single gene.

Polygenic Traits

Traits controlled by more than one gene.

Multifactorial Traits

Traits influenced by multiple genes as well as environmental factors.

Additive Model

A model predicting effects of individual genes on complex traits, assuming each gene has an equal effect.

Regression to the Mean

The concept explaining that extreme phenotypes tend to be closer to the average in subsequent generations.

Heritability

A measure used to quantify genetic contributions to phenotypic variation.

Concordance

The degree to which both members of a twin pair exhibit the same trait.

Single Nucleotide Polymorphism (SNP)

A variation at a single position in a DNA sequence among individuals.

Epigenetics

Chemical modifications to DNA or histones that alter gene expression without changing the DNA sequence.

Threshold Model

A model predicting that genotypes above a certain threshold will express an affected phenotype under specific environmental conditions.

Recurrence Risk

The probability that a genetic disorder will recur in families with a prior affected child.

Phenotypic Variation

Differences in phenotypes among individuals within a population, influenced by genetics and environment.

Twin Studies

Studies comparing the similarity of traits in identical twins to fraternal twins to estimate heritability.

Dizygotic Twins

Twins formed from the fertilization of two eggs, sharing about 50% of their genes.

Genetic Variance

Phenotypic variance in a population attributed to genotypic differences.

Environmental Variance

Phenotypic variance in a population attributed to environmental differences.

Haplotypes

A group of genes inherited together from a single parent that is used in genetic studies.

Obesity as a Multifactorial Trait

Obesity is influenced by multiple genetic factors in conjunction with environmental influences.

Genome-Wide Association Studies (GWAS)

Studies that identify associations between specific genetic variations and particular diseases or traits.

Leptin

A hormone that regulates energy balance by inhibiting hunger, which is encoded by the ob gene.