Central Dogma: Central Dogma

After wrapping up the discussion from the previous day’s lesson, we launched into an investigation of the process of Central Dogma.  Students learned how DNA codes for RNA which codes for protein.  We drew out the processes of transcription and translation, using a guided worksheet approach to help students understand what happens at each step of the process.  Whiteboard notes from two different classes are shown below:

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Notes from 2nd period
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Notes from 5th period

Updated: February 5, 2016

We completed the DNA base-pairing worksheet that we began yesterday.  We reviewed how DNA codes for RNA and RNA codes for protein.  We learned how RNA is read by ribosomes, with 3-base RNA sequences (codons) coding for specific amino acids.  Students were surprised to learn that that for many amino acids, there are more than one codons.  This was emphasized in questions 22 and 23 of the worksheet, where students learned to work backwards from a sequence of amino acids to figuring out one possible RNA sequence encoding that amino acid sequence, and finally figuring out the DNA sequence coding for the chosen RNA sequence.

Question 26 of the worksheet asked students to notice how amino acids with multiple codons often “wobble” at the third position (click here for a brief summary, or here for a not-so-brief summary).  The picture below attempts to add some context to the discussion.

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Parts of an amino acid, the basic unit of proteins
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Some amino acids are encoded in multiple codons because of what is known is the wobble position, or more formally as “degeneracy” of the genetic code.