##
* *Reflection: Gradual Release
Genetics - Introduction to Punnett Squares - Section 3: Students in Action

I really like the format of the student practice sheet. The educator who developed it used a format design that lent itself well to first model for students, then release the remainder of the problem set to students for completion.

The top half of the sheet reviews the fundamentals and serves as a reference for students as they complete problems on their own.

There is more to modeling for students then just making sure that they know how to answer the questions. Understanding the process and why it is an importance tool for genetics is also important.

Mastering Punnett squares requires practice in the application of new data and the ability to interpret the model noting the resulting genotypes, phenotypes and the probability of occurrence.

The Punnett square model is not an intuitive representation that students will be able to develop on their own. Modeling how visual representations can be used to make predictions and to communicate ideas is part of the process students must understand before we release students to practice on their own.

*Model & Practice*

*Gradual Release: Model & Practice*

# Genetics - Introduction to Punnett Squares

Lesson 3 of 8

## Objective: SWBAT use the basic vocabulary of genetics as it applies to creating Punnett Squares.

*60 minutes*

Students often confuse genetics terms. They need an opportunity to practice the application of terms to build fluency in using the vocabulary of genetics.

Scientists use Punnett squares to determine genetic outcomes for offsprings. Working with Punnett squares give students the opportunity to use the tools of scientists.

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Students will review the language of genetics as it relates to Punnett Squares. A Punnett square show students how genetic variation occurs in sexual reproduction. (**MS-LS3-2** *Develop and use a model to describe why asexual reproduction results in **offspring with identical genetic information and sexual reproduction results in offspring with genetic variation*.)

The Punnett square serves as a model to describe the cross-cutting concept of cause and effect. Students will be developing perseverance as they employ the use of the Punnet square, a tool used by scientists, to predict the resulting genotypes and phenotypes from various combinations of alleles. (**SP2** - *Developing and using models*)

Additionally students will apply mathematics as they use the Punnett square results to determine how likely it is to inherit a trait. (**MP4** - *Model with Mathematics*) (**6.SP.B.5 - ***Describing the nature of the attribute under investigation*)

This lesson was inspired by Sciencespot.net. The original student lesson sheet can be found on the Sceincespot.net in PDF format.

Trimpe, T. "Bikini Bottom Genetics." *Science Spot*. C. Trimpe, 2003. Web. Apr. 2015.

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#### Students in Action

*45 min*

*Students in Action*

We begin the lesson with definitions of genetic terms we will use in building Punnett Squares.

Students have worked with these terms in Genetics - Tour of the Basics so this introduction is a review. The vocabulary is still new to my students the reviews will help move them towards mastery.

We watch How Mendel's pea plants helped us understand genetics, a short TED-ED video, to help students understand how Punnett squares are used to predict outcomes in genetics.

I hand out the student practice sheet for this lesson. I have elected to use a resource prepared by another teacher because it is well done. The practice sheet is broken into sections. We first begin by reviewing vocabulary and then progress to the application of vocabulary as we complete Punnett squares. As a class, we complete the front side of the student practice sheet, then students complete the second page.

As we complete questions 3 and 4, I marvel at the use of the Punnett square as a model that helps us make predictions of genetic outcomes and the probability of occurrence. I share with students that models are an important communication tool in science to help ourselves and others visualize what is otherwise hard to observe.

Students are encouraged to check their work with a neighbor upon completion of the problems. The strategy to check in with a neighbor requires students to have completed the work themselves first. I instruct students that if they find they have different answers, each students should talk through their solution to the question defending their choices. They should begin with reading the question out loud. Sometimes, simply reading the question out loud provides clarity of understanding causing one or both of the students to have an aha moment and rethink their answer. The two students should evaluate the answers and determine how the question should be answered. It is possible that one or neither of the students has the correct answer. Their discussion should lead to a clear understanding of the question and a consensus for the answer.

In this video, I share how I mentor my students as they work on the Bikini Bottom Genetics practice sheet.

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#### Connecting the Learning

*5 min*

I ask my students, *How can genetics be so simple?*

The answer is that it is not. Mendel's experiments with peas were limited to the combination of recessive and dominate alleles. But there are exceptions to genetics that Mendel's rules do not explain. Alleles are not always dominate or recessive.

*Tomorrow, we will look at incomplete dominance, that is when an allele is neither dominate or recessive but the alleles combine to produce a third phenotype.*

*Take a look at the flowers. Combining a white flower with a red flower would produce a third phenotype giving us pink flowers.*

#### Resources

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Fantastic experience with betterlesson.com. Thank you very much!

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- LESSON 1: Genetics - Tour of the Basics Web Quest
- LESSON 2: Have Your DNA and Eat It Too!
- LESSON 3: Genetics - Introduction to Punnett Squares
- LESSON 4: Genetics - Incomplete Dominance
- LESSON 5: Finding a Gene on a Chromosome Map
- LESSON 6: Stem Cells Web Quest
- LESSON 7: Cloning Web Quest
- LESSON 8: Stem Cells or Cloning - You are the Expert!