Reflection: Grappling with Complexity Amplification of Genomic DNA - Section 1: Introduction


I have never truly been a fan of analogies so you can imagine my horror when I began teaching biotechnology and found many well-meaning analogies created to bring a study of molecular biology to school-aged children. One of the analogies that I find particularly unsettling is the oversimplification in the comparison that states that, "PCR is like putting DNA in a photocopier"! No........Actually though most of the DNA yield at the end of amplification is identical these new molecules are not simply a "picture" of the genetic code they are more like a "blueprint" or a "template" which are able to go forth and make other originals! This is not true of the product that emerges from a photocopier! 

In my research of the use of analogies in science I ran across these best practices and had to share. There are other people out there that are most likely feeling my pain and that is comforting! Enjoy...

Tests an analogy should meet:

1. The analogy should compare the unfamiliar to the already-familiar. The analogy of currents to the flow of water in pipes is useless unless the student already has a good grasp of hydraulics.

2. The analogy should be simple and easy to present. If the comparison requires elaborate justification or explanation, forget it. If the analogy requires a long list of "exceptions" and qualifications, the time would be better spent on a direct and fuller physical and mathematical treatment.

3. The analogy should be reasonably complete in all important details. The non-analogous details shouldn't require elaborate explanation.

4. The analogy should be mathematically analogous. The two cases being related ought to obey the very same mathematical equations.

5. The analogy should be physically analogous. The physical principles in the cases being compared ought to also be meaningfully analogous.

6. Analogies ought never be represented as a demonstrations, arguments, or proofs. Analogies must never replace rigorous mathematical and physical development.

7. The analogy should not be restricted to a single case or a special case.

8. All obvious extrapolations of the analogy should be valid. The analogy should continue to give correct predictions in other cases that will occur in the course, and other cases that a thoughtful student might apply it to.

9. There should be no hidden or unstated assumptions required to make the analogy "work."  

  Clear as MUD: Why the Use of the Wrong Analogy Can Make Matters Worse!
  Grappling with Complexity: Clear as MUD: Why the Use of the Wrong Analogy Can Make Matters Worse!
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Amplification of Genomic DNA

Unit 8: Nobel Prize-Winning Biotechnology
Lesson 7 of 9

Objective: Students will be able to collect a DNA sample from their own cheek cells and use this sample to amplify a gene of interest.

Big Idea: Explore one of the most powerful techniques in molecular biology.

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1 teacher likes this lesson
Science, Biotechnology, DNA Technology
  170 minutes
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