Inheritance Patterns (#2 of 6): Incomplete Dominance

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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 (click here to link to lesson) 

b)    Incomplete dominance (focus of this 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

I direct students to this document: Punnett Squares Packet

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.

Punnett Squares Packet: Introduction Section

Secondly, do a class reading of the introductory reading section (p. 1). I do this to differentiate the different coding (nomenclature) conventions used among the four main inheritance patterns (against the system that was originally learned). Based on this information we tackle the second inheritance pattern (Incomplete Dominance pp. 1-2). As need be, this document (Solving Punnett Squares) may be projected where all students can see it for the purposes of problem solving.



Instructional Input/Student Activities

35 minutes

Teaching Challenge: How do I support students to develop and use scientific models? 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.

Punnett Squares Practice packet (Incomplete Dominance pp. 1-2)

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

Teaching Challenge: How do I develop routines and procedures to support students to work independently in the science classroom?  

(Addressing both teaching challenges)

I work problems #1-4 together with students 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.

Then students will complete #5-15 on their own. As for the independent aspect, students are grouped into tables of no more than four students. There is a particular set of roles and responsibilities for each member (leader, spokesperson, recorder, and manager). Before students solicit my help, they are to go through the "chain of command": first ask your table partner(s) then ask your team leader and then, if still stuck, ask the teacher.

I am guilty of "bailing kids out" too early and I have tried to halt this tendency (with clearly benevolent intentions but many times debilitating effects; they aren't able to stand on their own). So as a stop-gap, the structure of the team limits this occurrence while still providing a life-line for struggling students.

In light of this, I roam the class checking that students are faithfully following the full process and being on hand to help students as needed.

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

5 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 Genetics assessment (only questions #3 & 4)