BIOL 321 Chapter Notes - Chapter 5: Human Height, Intelligence Quotient, Leptin
Document Summary
Discontinuous variation phenotypes that fall into two or more distinct non-overlapping classes: the tall and short phenotypes in mendel"s pea plants are an example of discontinuous variation. Analysis of such traits is complicated by the by the fact that often each gene contributes only a small amount to the phenotype, and the environmental components can be hard to identify and measure. Complex traits can be fully understood only when all the genetic and environmental components are fully identified and their individual effects and interactions have been measured. In traits controlled by two or more genes, a small number of the offspring have phenotypes identical to the p1 generation. Most f2 offspring, however, have phenotypes between those extremes; their distribution follows a bell-shaped curve, with each gene adding a small but equal amount to the phenotype. Complex traits have several distinguishing features: traits are usually quantified by measurement, rather than by counting, two or more genes contribute to the phenotype.
