Polygenic Inheritance: Definition & Examples

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  • 0:00 Patterns of Inheritance
  • 0:38 Genetics Review
  • 1:20 How Polygenic…
  • 2:40 Real-World Examples
  • 3:14 Lesson Summary
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Lesson Transcript
Instructor: Dominic Corsini
In this lesson you will learn how traits like your height, weight, hair color, and skin pigmentation are determined by the complex interaction of several different genes in a process called polygenic inheritance.

Patterns of Inheritance

Most people remember taking a high school biology class. In that class, you may have discussed the inheritance of different traits, physical characteristics, and genes, which are sections of DNA that code for traits. Generally, most introductory biology courses talk about dominant and recessive traits. However, humans have slightly more than 20,000 genes and most of the traits are not simply dominant or recessive. Instead, many of our traits are passed from parent to offspring through other, more complex patterns of inheritance. One such pattern, and the focus of this lesson, is called polygenic inheritance, which is when a trait is influenced by more than one gene.

Genetics Review

What does it mean to say that a trait is influenced by more than one gene? Well, to answer that question we must first examine some background information. For starters, let's assume we're studying a hypothetical gene for color in flowers. Suppose there are two versions of this gene: one version that makes red flowers and another that makes white flowers. These different versions of a gene or the trait for which they are responsible are called alleles. When applying this terminology to certain human traits, such as hair color, we say there are many different alleles that determine coloration. Think about it. Do people only possess dark hair or light hair? Of course they don't. There is variation in our hair color because of the numerous alleles combining to determine it.

How Polygenic Inheritance Works

Now, let's take this background knowledge and apply it to understanding polygenic inheritance. For our example, we'll turn our attention back to our hypothetical red and white flowers. If the trait were passed along via polygenic inheritance, its appearance would be determined based on several different genes, and as a consequence, several different alleles.

Polygenic Inheritence

This illustration presents a hypothetical polygenic pattern of inheritance for flower color. In this example, rather than having one gene control flower color, the interaction of three genes is responsible (as designated by the letters A, B, and C).

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