Predicting Trait Inheritance

Contributor: Hannah Brooks. Lesson ID: 12789

Mom has blue eyes; Dad has brown. One has blond hair, the other red. Will their child have one brown, one blue eye and striped hair? Learn how scientists try to predict what traits children will have!

categories

Life Science

subject
Science
learning style
Visual
personality style
Lion
Grade Level
Middle School (6-8)
Lesson Type
Dig Deeper

Lesson Plan - Get It!

Audio:

How do meteorologists predict the weather days in advance? What does that have to do with the color of beans?

Meteorologists use probability to estimate what weather patterns will move into an area.

They base their predictions on what has the most likelihood of happening. They develop a guess that is based on factual information and historical trends. Scientists can use probabilities, or chances, to determine the likelihood that offspring inherit specific traits.

In the previous Related Lesson in our Human Inheritance series, found in the right-hand sidebar, you learned more about how physical appearance and genetic make-up are related. You also learned that some traits are considered dominant and can hide recessive alleles. Scientists can use all of this information to make predictions about how traits are passed to offspring using a tool called a "Punnett Square," shown below:

punnett square

Image by Pbroks13, via Wikimedia Commons, is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.

These simple tools allow scientists to illustrate how alleles separate out during cell division and possible recombination during fertilization.

As you watch a quick video on Punnett Squares, record the following on a sheet of paper:

  1. How are dominant and recessive alleles related?
  2. How are the mother and father represented in the Punnett Square?
  3. Fill out a Punnett Square:
   
   

 

Watch Mahalo's Learn Biology: How to Draw a Punnett Square to find the answers:

 

Punnett Squares can only be used for simple trait inheritance, and cannot show us complex combinations of traits or characteristics. Each box in the Punnett Square represents a 25% chance that the offspring has that genotype. Remember that dominant alleles will mask recessive alleles. If an offspring has the heterozygous genotype, they will have the dominant phenotype.

We will get more practice with these ideas in the Got It? section of this lesson. Before you move on, explain how Punnett Squares can be used to predict inheritance to a parent or teacher.

  • Can scientists always use Punnett Squares to predict traits and characteristics?
  • How might these tools be helpful for scientists and geneticists?

Continue on to the Got It? section create your own animal using a Punnett Square!

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