The Central Dogma (#5 of 6): Translation

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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:

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

I hope you get some value from my work!

Anticipatory Set ("Hook")

10 minutes

Click here for the previous lesson in the series.

Peer Instruction Protocol (PIP): Leveraging an individual and group-oriented review strategy.

Yesterday's instruction focused on the relationship between the different forms of genetic material (DNA and RNA) and the mechanism and purpose of transcription. At this point I want to reflect on whether students learned what I intended. I regularly make use of the PIP review strategy as a way to assess student learning. A more detailed explanation is provided here.

I will progress through this review activity in stages and following each major topic taught in the near past. In this case, I will address only questions #7-10 (Transcription).

Instructional Input/Student Activities

35 minutes

Central Dogma Notes (slides #13-23)

In this segment of the lesson, I spend some time using the strategy of direct instruction using the Cornell note-taking method. The topic is DNA replication and the context is to compare and contrast mitosis with meiosis (previously studied in this series).

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

Students should recognize that the fate of the mRNA molecule is already largely determined. The rest is just history. Once the transcript enters the cytoplasm and joins with the rRNA, tRNA and its associated amino acid, the process becomes a bit autonomous. mRNA is read and amino acids are assembled in synchrony.

Once again, students should recognize that the relationship between chemical bases on both DNA and RNA nucleotides is that they are complementary for both the DNA-DNA relationship (replication) and DNA-mRNA relationship (transcription), and mRNA-tRNA relationship (translation). By knowing the rules for base-pairing (pattern) students will be able to predict the complementary protein sequence of the protein chain. The question now is more complex than "How does the (DNA) genotype morph into the (protein) phenotype?" It now becomes "What happens when the original DNA code is altered (mutated)?" This can be determined only by completing the translation process and it requires knowledge of the "Decoder Wheel" featuring the 64 triplet mRNA codons that are read by tRNA and associated amino acids inserted as instructed. Sometimes a DNA mutation will result in a substituted amino acid (relative to the original plan) and sometimes not. And...sometimes the substituted amino acid causes a phenotypic change and... sometimes it does not which makes for interesting conversation over coffee! What can I say? I'm from Seattle and what doesn't go well with coffee! =)

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

10 minutes

Central Dogma Review

As we wrap up for today, I direct students to complete remainder of p. 2-3 (remainder of "translation" questions) to apply what they learned. This review packet will be completed in several stages as we progress through this lesson series. 

The answer key is provided for your reference. Click here for a sample of student work.

Click here for the next lesson in the series.

Lesson Extension & Follow-Up Activities

Students will be directed to finish the assigned questions from the Central Dogma Review packet if they did not do so in class.