Inheritance Patterns (#5 of 6): Pedigrees

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Objective

1. Students will 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 (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. (focus of this 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 can I develop a classroom culture that encourages student engagement, curiosity, and a desire to understand the world through scientific exploration?

The short answer is to draw in the study of real life issues that blend with politics, history, art and other fields of interest. Not all of my students are super gung-ho about science but if I can engage them in seeing the interconnections among and between disciplines I just might hook them enough to grow in their "scientific literacy" quotient!

The Bolshevik Revolution and the Missing Romanov Children

Open up class with a video that overviews the mystery of the Romanov family’s fate and that of Anastasia. For more than 70 years the case of young Anastasia Romanov's fate and identity had been headline news. This human interest story serves as the hook to using science to solve very real problems. This segues into the topic of pedigrees and, if time and interest exist, could flow into the interesting and poorly understood topic of mitochondrial DNA and its role in linking maternal lines across many generations.

Instructional Input/Student Activities

35 minutes

This is not your dog's kind of pedigree here! Typically the first association students make to the term. =)

Teaching Challenge: How do I support my students to compose, communicate, and evaluate a clearly stated, evidence-based, compelling argument?

 There are four basic inheritance patterns revealed in a family's pedigree:

1. Autosomal Dominant

2. Autosomal Recessive

3. X-linked (sex-linked) recessive

4. X-linked (sex-linked) dominant

(Less commonly addressed: Y-linked (sex-linked) recessive)

The challenge for students is to learn the clues to look for when trying to deduce the proper pattern in a given unknown pedigree. The trick is to propose various hypotheses about the pedigree and work out the possible genotypes to learn which most reasonably fits with the data. This, in essence, is the inquiry process and their argument (claim in favor of pattern #1, 2, 3, or 4) must be evidenced. Therefore, the necessary scaffolding toward that end goal is the work of today.

Punnett Squares Practice Packet (Pedigree Problems pp. 11-12)

  1. Distribute Pedigree Patterns and briefly review the key characteristics of the various inheritance patterns. Note: This document does not explicitly address pattern #4 however it is basically the reverse of X-linked recessive (with both males and females possessing the trait in generally the same ratio).
  2. Work problems #1-6 on p. 11 with students while soliciting student input for answering questions.
  3. Assign the remaining problems for independent/pairs work.

Note: This video may assist you in working through the various hypotheses that lead to the best solution for the problem.

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 #9 & 10).

Check out one of the pedigree questions posted in class and an ensuing small group discussion about pedigrees.