Define the following: (a) polygenic, (b) additive alleles, (c) correlation, (d) monozygotic and dizygotic twins, (e) heritability, (f) QTL, and (g) continuous variation.

Key Concepts

Polygenic Traits

Polygenic traits are characteristics that are influenced by multiple genes, rather than a single gene. This means that the phenotype, or observable traits, results from the cumulative effects of several alleles, each contributing a small effect. Examples include height, skin color, and intelligence, where variations arise from the interaction of many genes.

Additive Alleles

Additive alleles refer to alleles that contribute to the phenotype in a cumulative manner. In polygenic traits, each allele adds a certain amount to the overall trait expression, leading to a continuous range of phenotypes. This concept is crucial for understanding how traits can vary widely within a population due to the combined effects of multiple genes.

Heritability

Heritability is a measure of how much of the variation in a trait within a population can be attributed to genetic differences among individuals. It is expressed as a proportion, ranging from 0 to 1, where a higher value indicates a greater genetic contribution. Understanding heritability helps in assessing the potential for traits to be passed on to future generations.