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How to Use a Punnett Square Lesson for Kids: Definition & Examples

Instructor: Caroline Ebeling

Caroline is a bilingual (Spanish and English) teacher and a trilingual (Spanish, English, and French) children's book author with a master's degree in bilingual education.

Have you ever wondered why you're the only person in your family with blue eyes? Or where your brother got his bright red hair? enetics! In this lesson, we'll learn how to predict genetic traits, such as eye and hair color, using a Punnett square.

Have you ever wondered why you're the only person in your family with blue eyes? Or where your brother got his bright red hair? Genetics! In this lesson, we'll learn how to predict genetic traits, such as eye and hair color, using a Punnett Square.

Genes

Imagine seeing a family walking down the street. Mom and Dad have brown hair. Their daughter also has brown hair. But the baby boy has blonde hair! Why don't they all look alike even though they are related? This happens because of genes (pronounced jeans). Even though this word sounds like a pair of pants we have in our closet, these genes are very different.

Genes are special parts of our unique DNA that give information to the cells in our bodies. In other words, genes tell our bodies what we are going to look like! The genes in our DNA come from our parents. However, this doesn't mean you will have the same genetic traits, such as eye color or hair color, as your mom or dad. Everybody's genes are a unique combination.

The genes in our DNA determine our characteristics, or traits, such as hair or eye color.
Genes

Recessive and Dominant Genes

There are two types of genes that you get from your parents for every genetic trait: recessive and dominant. Recessive genes are genes that aren't as likely to show up as a trait. For example, it is not as common to have blue or green eyes. These are recessive genes that are likely to be overruled by dominant genes. Dominant genes are more common and more likely to show up as a trait. If your dad gave you the recessive blue eye gene, and your mom gave you the dominant brown eye gene, you would have brown eyes. Dominant always beats recessive!

Punnett Square

In order to truly predict hair or eye color, you would have to think of the genetic traits of your parents, your grandparents, and even your great-grandparents! Why? Even though some people have dominant traits, like brown hair or eyes, it doesn't mean that they don't also have some recessive genes in their DNA. They might just not be in use! Even though your mom and dad might have dominant traits, they can still pass on recessive genes to you!

Scientists figure out the probability, or likelihood, of someone's genetic traits using a Punnett square. This diagram helps us to see what traits the child could have based on the different combinations of the parents' genes. For example, let's imagine that your mom has brown eyes, but your grandfather has blue eyes. Therefore, your mom's genes are represented as Bb. The uppercase B is for her dominant trait of brown eyes, but in her DNA, she also has a lowercase b (recessive blue eyes) that was given to her by her father.

Let's say your dad has blue eyes. Blue-eyed people are always represented as two lowercase letters because they have been given two recessive genes. Your dad's parents must have blue eyes, and they passed the recessive trait to their son. Therefore, your dad is represented as bb.

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