The Central Dogma (#1 of 6): Genetic Material

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Objective

Systems of specialized cells within organisms help them perform the essential functions of life. (HS-LS1-1) All cells contain genetic information in the form of DNA molecules. Genes are regions in the DNA that contain the instructions that code for the formation of proteins, which carry out most of the work of cells. (HS-LS1-1 & HS-LS3-1)

Big Idea

The structure of DNA is a double helix. Its shape explains how hereditary information is stored and passed along to offspring.

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.

With regard to this particular lesson, students will:

1. understand that cells store and use genetic information to guide their functions. Furthermore, the structure of DNA is a double-helix. Its shape explains how hereditary information is stored and passed along to offspring.

2.  know that all cells contain genetic information in the form of DNA molecules. Genes are regions in the DNA that contain the instructions that code for the formation of proteins, which carry out most of the work of cells. (HS-LS1-1 & HS-LS3-1)

From the perspective of instructional strategies, I want to emphasize the following challenges:

How can I develop a classroom culture that encourages student engagement, curiosity, and a desire to understand the world through scientific exploration?

Teaching Challenge: How can I develop my students’ ability to apply unifying ideas to make connections across science content (among and between physics, chemistry, biology, earth and space science)? 

I hope you get some value from my work! Please find the more intricate details of this lesson plan there.

Anticipatory Set ("Hook")

5 minutes

Parking Lot Entry Prompt:  “DNA is _____.” & “DNA is not _____." 

At this point, students will have had exposure to the topic of DNA (to some degree) by virtue of media and prior classes. I try not to assume what students may or may not know so to get started I prompt students to use a Post-It note to describe what they know (or think they know) about DNA in a positive sense. For example, a student might state that DNA is a type of evidence used in court cases or that it is a helical molecule.

Then they are to write what DNA is unlike, such as it is not the same for every person. This follows the format of "example" and "non-example" found in the Frayer Model of academic vocabulary instruction. They are to use one color of ink for now and then I will have them revisit it at the end of class in another color.

How can I develop a classroom culture that encourages student engagement, curiosity, and a desire to understand the world through scientific exploration? I use the strategy of the open-ended question to generate the widest possible pool of responses in both the introductory and wrap-up entries to this Parking Lot prompt. The intent is to cull some of these responses from the class to share out at the start of class (either the next day or soon thereafter). My plan is to have students appreciate the wide variety of responses generated from their peers and, time permitting, I will conduct a brief discussion about the responses such as "How can this be investigated?", "What question(s) might you ask about 'so-and-so's' response?" or "Why might ________ be significant to one's life?"

Instructional Input/Student Activities

45 minutes

The primary objective for today is to have students explore the structure and function of genetic molecules; primarily DNA and RNA. In doing the Double Helix Coloring Activity students will read about the way nucleotides are built in a basic sense, the similarities and differences between DNA and RNA nucleotides, the locations in the cell where they can be found, and what their functions are. Additionally, there is a fair amount of color-coding of nucleotides and how they are built (sugar-phosphate-base) which will be relevant as we unpack the process of protein manufacture. All of the remaining instruction in this series featuring the "Central Dogma" hinges on this basic understanding. 

The overarching question students will grapple with is, "How does the invisible genotype (DNA-based gene segment coded as "AA" or "Aa" for example) transform into the visible phenotype (such as hair or eye color)?

The teaching challenge here is to connect the previous unit of study (Genetics) that has a macro focus with this study of molecular genetics with micro focus. If successful, students will have shown the ability to apply unifying ideas to make connections across these two related science topics.

That is, the structure and function of microscopic molecules has a potentially significant impact on the behavior and expression of the DNA code. Other important cross-cutting concepts include: pattern recognition (relationship between DNA codons, the complementary mRNA codons and resulting chain of amino acids); viewing the cell as a model system with subcomponent parts (nucleus and cytoplasm); and the potential cause and effect relationship between mutation and changes to the phenotype.

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

5 minutes

Parking Lot Entry Prompt:  “DNA is _____.” & “DNA is not _____." 

Having described the nature of DNA at the beginning of the class, students will be asked to use a color of ink (other than that used at the start of class) to revisit the prompt given. In this instance they are to add (and potentially clarify or correct) what they learned from the activity. Students will then post these responses on the board so that I can review them and share some of them with the class the following day.

Click here for the next lesson in the series.

Lesson Extension & Follow-Up Activities

Students will be directed to finish the DNA Double Helix Coloring Activity if they did not do so in class.