Mendel's Law of Segregation: Lesson for Kids

Instructor: Corrie Boone

Corrie holds master's in elementary education, taught elementary ESL in the public schools for 5 years, and recently was teaching EFL abroad.

You probably know you got everything from your eye color to the shape of your tongue from your parents. But did you know that Mendel's Law of Segregation is what determines if you get a tongue like your mom or your dad? Let's learn all about it!

The Father of Genetics

Do you have blue or brown eyes? Straight or curly hair? Brown or blonde hair? These traits are characteristics you inherit (or get) from you parents. Specifically, there are genes, like a code, in your DNA that determine blue or brown eyes, and studying heredity (which genes you inherit) is called genetics.

The scientist Gregor Mendel is considered the father of genetics because he made the first major discoveries in how genes and their characteristics are passed from your parents to you. Mendel used pea plants in his garden to study inheritance. In this lesson, we're going to look at the experiments Mendel performed that led him to his Law of Segregation and the explanation for gene inheritance.

Mendel's Experiments

Mendel studied seven characteristics of pea plants: seed color, seed shape, flower position, flower color, pod shape, pod color, and stem length. For the sake of understanding in this lesson, we're just going to look at the results he got when he followed the heredity of the flower color. Mendel's experiment had three basic steps.

  1. First, he created a parent generation (P) of true-breeding plants. The flowers of a pea plant can be purple or white. So, a true-breeding purple plant would always produce a purple plant when it self-fertilizes, and the same for a white plant. Self-fertilizing just means it produces on its own, which most plants can do.
  2. Second, Mendel cross fertilized true-breeding purple plants and true-breeding white plants (F1 generation). Surprisingly, 100% of the plants were purple. Mendel named the visible characteristic (purple flowers) the dominant trait and the invisible characteristic (white flowers) the recessive trait.
  3. Third, Mendel self-fertilized the F1 generation plants, making the F2 generation. Once again, the results were quite interesting. When allowed to self-fertilize, 75% of the plants were purple (dominant trait) and 25% were white (recessive trait). You can look at the chart to help you better understand these steps.

And when Mendel performed the same experiment with the other six characteristics mentioned above, he got the same results: 75% dominant and 25% recessive.

mendels experiment

Law of Segregation

Mendel's findings from his experiment led to the law of segregation. Each person has two genes that determine every characteristic, like hair or eye color (or, in the case of those plants, flower color). Your mother has two genes for her eye color and your father has two genes for his eye color. But you only get one from each. The law of segregation says that the one you get from each parent is random.

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