Inheritance Patterns (#1 of 6): Punnett Sqares

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1. Students will be able to apply concepts of statistics and probability to explain the variation and distribution of expressed traits in a population. (HS-LS-3) 2. Students will understand that cells store and use genetic information to guide their functions. An organism’s genotype determines its phenotype. These traits can be dominant or recessive depending on the alleles found on their genes.

Big Idea

Nearly all human traits, even many diseases, are inherited in predictable ways. Using the tools of mathematics and modeling, these inheritance patterns can be properly deduced.

Learner Goals

Note: I recommend that you first check out this resource in order to get the most out of this lesson!

In high school I took several drafting classes and, for a while, I had hoped to become an architect. With respect to planning instruction and teaching, I feel that I can still live out the detailed approach to building something intricate and complex even though the product is a lesson rather than a certain "built environment".

The lesson-planning document that I uploaded to this section is a comprehensive overview of how I approach lesson planning. This template includes the "Big Three" aspects of the NGSS standards: Disciplinary Core Ideas, Crosscutting Concepts, and Science Practices. Of course, there are many other worthy learning goals, skills, instructional strategies, and assessments that can be integrated into a class session. I don't feel compelled to check every box but, rather, use it as a guide to consider various options and tailor the lesson in light of these. Furthermore, for the bigger picture of this unit of study please refer to this document.

With regard to this particular lesson (as part of the series) students will be able to...

1. Explain how are traits passed from one generation to another and why do members of the same family have different traits.

2. Explain why some traits are hidden in one generation and expressed in the next.

3. Apply concepts of statistics and probability to explain the variation and distribution of expressed traits in a population. (HS-LS-3)

4. Solve monohybrid (one trait) and dihybrid (two trait) cross problems (AKA Punnett Squares).

a)    Complete dominance (focus of this lesson)

b)    Incomplete dominance (click here to link to lesson)

c)    Co-dominance (e.g. ABO blood types) (click here to link to lesson)

d)    Sex-linked (e.g. colorblindness and hemophilia) (click here to link to lesson)

5. Interpret a pedigree and the symbols used to represent males, females, affected and unaffected individuals. (click here to link to lesson)

6. Make and defend a claim for the inheritance pattern(s) found in a given pedigree. (click here to link to lesson)

I hope you get some value from my work!

Anticipatory Set ("Hook")

10 minutes

Beyond the nuts-and-bolts of the content in this lesson (and the larger series), there are very real and pertinent teaching challenges that, when properly addressed, will lead to great interactions and learning opportunities among and between my students and myself.

I hope to clearly convey my strategies to face these head-on.

Teaching Challenge: How do I develop routines and procedures to support students to work independently in the science classroom? Engagement for all students is the daily goal for both my students and me. There is no concept of "taking a day off" from learning. I use and the Random Draw strategy as I interact with my kids and in doing so students never really know when their turn comes up until I call on them. Secondly, I firmly believe that "Failure is an option, but it is not the best one available." In other words, we can and should learn and grow from our failures. This is addressed very explicitly in my class early on in the year. As we begin the process of learning the method of Punnett Square models, I review the basics of the Monohybrid Cross Worksheet as a class. As I call on students and they correctly answer the prompt/problem, their card goes to the back of the deck. If, however, they do not then I go to the next card and then return back to him/her who missed. This may seem simple but the message is clear:

  • all students are capable to demonstrating their ability to know, understand, and do something.
  • It also lets them know that I believe in their capabilities and that all of us are accountable (in big and small ways).
  • It is also a confidence booster for kids who typically are the silent and unseen among a classroom.

Teaching Challenge: How can I increase/improve my students’ use of appropriate and precise scientific vocabulary?

Word Wall: Building on the basic vocabulary from yesterday, I review key vocabulary with students that will differentiate today's content from the others in the series:

  • complete dominance (yesterday)
  • incomplete dominance
  • co-dominance (coming days)
  • sex-linked (coming days)

I direct students to their copy of the learning goals for the unit for clarification (pp. 2-3) and Quizlet vocabulary (pp. 4-5). These represent the Learner Outcomes for basic genotype and phenotype combinations students will master.

Instructional Input/Student Activities

35 minutes

Teaching Challenge: How do I support students to persevere and grapple with complex tasks? 

Teaching Challenge: How do I support students to develop and use scientific models? (Addressing both teaching challenges) In conjunction with incorporating podcasts into the framework of my homework expectations, I intentionally carve out time for modeling and practice of concepts in class (a la the Flipped Classroom model) as well as formative assessment of those concepts addressed therein. In this particular segment of today's lesson, students should have (heavy emphasis due to the fact that not all do so) become familiar with the steps to Solving Punnett Squares problems.

Regardless, by scaffolding (for the whole class) the various needed knowledge and skills will go a long way to shepherding students to meeting standard in this area. Using the Solving Punnett Squares file as a class visual and the Monohybrid Cross Worksheet, I explicitly teach the seven-step process by which a Punnett Square problem can be solved.

As a class I model the process of solving problems #16 a, b as I randomly solicit student input during the problem-solving process. At this point, I assume that students have a very basic understanding of the process therefore I hold them to following all seven of the steps. With more experience, they may choose to condense a few of the steps for efficiency however.

Students are then to work problems #17-21. As they do so, I roam the class checking that students are faithfully following the full process and being on hand to help students as needed.

Again, for those who do follow the podcasts at home, their understanding is enhanced and those who choose otherwise are still getting the basics.  Self-directed instruction at home and problem-solving as independent and interdependent learners in class; that's the philosophy!

Closure: What did we learn? Where do we go from here?

10 minutes

Formative assessment is crucial for getting that "dipstick" measurement of student learning. There are a great many ways in which this can be done. One of the more recent and very transformational strategies I have used is called the Peer Instruction Protocol first devised by Dr. Eric Mazur.

Peer Instruction Protocol (PIP) 

As a wrap-up for today, I conduct the review using the PIP assessment (only questions #1 & 2)