Apple Doesn't Fall Far From the Tree - A Tree of Genetic Traits
Lesson 9 of 19
Objective: SWBAT create a visual representation of the frequency of trait combinations within the population of their classmates.
This lesson is part of a unit that addresses the following Life Science Disciplinary Core Idea:
LS3 - Heredity: Inheritance and variations
The performance expectations in LS3 help students formulate an answer to the question, "How do living organisms pass traits from one generation to the next?"
This lesson introduces students to genetic diversity. This lesson will give students the foundational knowledge to be able to successfully complete the following performance expectation and cross cutting concept:
- 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.
- Cause and Effect: Caused and effect relationships may be used to predict phenomena in natural systems.
To engage students in today's lesson I show the Staff Takes Supertaster Test video to introduce students to the idea of being a Supertaster. The ability to taste PTC (a Supertaster) depends on someone having the dominant form of the trait. This previews the activity they will complete in the explore section of the lesson.
I have students record the percentage of persons shown to be a Super Taster. Once students have calculated the percentage, I have students make a hypothesis for the question, "Am I a Supertaster?" Some great teaching tips in developing students' writing of hypothesis can be found on Science Buddies.
I record the number of persons who believe they are Supertasters, which we will compare with actual tasters after we complete the explore activity.
Students begin their exploration by completing a Traits Tree activity courtesy of the Genetic Science Learning Center.
Traits Tree Activity
In this activity students explore inheritance by completing a fun and engaging hands-on-activity. In this activity students are able to visually see how their genetic traits compare to that of their classmates. Students determine which version of the trait they have for the following genetic traits: Earlobe Type, Ability to taste PTC, and Tongue Rolling.
Traits are observable characteristics that are passed down from parent to child.
An individual will have many traits they share in common with others.
An individual’s overall combination of traits makes them unique.
Some traits are more common in a population than others.
PTC paper, leaves, tape, scissors, transparencies or large butcher paper
1. Ideally this lesson should be completed after you have completed Heredity: An Inventory of Traits. In this activity students inventory a variety of traits including two of the traits needed for this activity (Earlobe Type, Ability to Roll Tongue). As a result students are able to check of the appropriate boxes in their Leaves.
2. In terms of PTC paper, students are given a little piece to gently place in their tongues. Students are given instructions that the degree of taste varies among people from non-taster, mild taster, to super-taster. Once students have determined if they indeed are a taster they are instructed to throw out PTC strip into trash.
3. Once students have determined all three traits they are called one by one to place their Leaves on our class Tree Large Format. It is important to model how to determine what the correct tree branch is for their placement. I model this by placing my leave on the genetic tree. In addition it's also important to point out that students should not cover the pre-printed labels on the branches since they guide students to the correct branch. Depending on class you may want to call students one by one making sure they place leaf on the correct branch or sending teams all at once.
4. Once all student leaves have been placed on tree its important to have a discussion with class on patterns that they notice. Some possible guiding questions are the following:
- What branch has the most leaves?
- What 3 traits does that tree represent?
- In terms of inheritance what does this tree give you insight to?
- If you were to do this activity at home with your family members what would you expect your genetic tree to look like? Why?
- How do you think the genetic tree would appear if we did this in another part of the world?
In this section of lesson I introduce students to Mendelian Genetics by showing them a video that answers a very common question, "Why do we look like our Parents?"
This video introduces students to Mendelian Genetics and Punnett Squares, which will be covered in greater detail in upcoming lessons.
As students watch the video they answer the following questions in their science interactive notebooks, once student have answered questions individually, they share their answers with their cooperative groups. Students are grouped in team of 4 (High, High Middle, Low Middle, Low)
1) What is genetics?
2) Why is the name of the molecule that is the focus of genetics?
3) Why is Gregor Mendel important to the study of genetics?
4) Write down the Pedigree Chart show in video.
5) What was surprising about the results Gregor Mendel got when he crossed yellow and green pea pods, short ant tall pea plants?
6) What is a dominant and recessive trait?
7) According to video why do we look like our parents?
In this section of lesson students elaborate on what they have learned by reading a text on Genetic Basis of Butterflies, sourced from ReadWorks.
The objective of this text is for students to learn that there is genetic diversity across all species and that that genetic diversity has benefits in terms of evolution.
Topics Covered in Text
1. Genetic Traits
2. Genetic Diversity
4. Evolutionary benefit of traits
Once student have read article, students are required to answer text-dependent questions found at end of text. (RST.6-8.1 - Cite specific textual evidence to support analysis of science and technical texts.)