What is a quantitative characteristic? (with photo)

Scientists working in genetics often use the term “polygenic inheritance” when characterizing the formation of a quantitative trait.

In genetics, a quantitative trait is one that varies in its characteristics and expressions. Two or more genes, along with environmental interactions, are usually responsible for the ultimate expression. These characteristics are described in numbers and may vary in degrees. Most quantitative features are continuous and often do not fit into any discrete categories. The study of the inheritance of such traits is called “Quantitative Genetics”, and such phenotypes in humans include – but are not limited to – height, intelligence quotient (IQ) and blood pressure.

When scientists know a genotype or the internal genetic code of a specific trait, they can predict the resulting phenotypes or external traits of that trait. They are called discontinuous features and are assigned to discrete classes. Not all features, however, fall neatly into a discrete classification, but instead are continuous and difficult to predict. These types of characteristics are called quantitative characteristics because they are usually recorded as distributions of numbers.

Polygenic inheritance is the term used by scientists to describe the formation of a quantitative trait. Genes that influence the value of quantitative traits are referred to as quantitative trait locus (QTL). Quantitative trait formation involves two or more genes that contribute to a phenotypic trait and often also involves interaction with the environment. Height in humans, for example, involves several genes; however, final gene expression is affected by environmental factors such as available nutrition. Rather than following a specific pattern, characteristics vary along a continuous gradient that is usually illustrated in a bell curve.

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Numbers and percentages are the main methods of documenting quantitative characteristics. Numerical values ​​of quantitative characteristics are often ordered from highest to lowest and represent a continuous order rather than a specified count along a continuous gradient. Quantitative characteristic values ​​usually differ only by small, arbitrary amounts, not by fixed amounts. Therefore, most scientists assume continuous data rather than specific values ​​or counts when documenting quantitative characteristics. Scientists try to predict the variance of a quantitative trait to find the distribution mean and describe the spread on a bell curve.

Expressions of quantitative traits appear in almost all organisms, usually mainly in plant and animal life. In plants, examples include crop yield, color distribution, and disease resistance. With animals and people, weight, height, learning ability and even blood pressure are expressed as a quantitative characteristic.

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