Tag Archives: DNA

Evolution: Evolving Bodies, Evolving Switches

Today, students watched the HHMI Biointeractive video titled Evolving Bodies, Evolving Switches (watch below).  The video explains how the stickleback fish has evolved and adapted to its environment, and shows how scientists are using genetics to further understanding of evolution as well as developmental biology.  After watching the video, students completed a worksheet to reinforce and extend their learning.

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.

Central Dogma: Procedure Quiz

Students had the opportunity to demonstrate proficiency in the skill of writing a Procedure.  They were provided with an EOC-style procedure writing task directly related to the strawberry DNA extraction experiment from yesterday.  During the last 15 minutes of class, students watched the Stranger Visions video to learn how their human DNA can be used to construct 3-D printed models of faces.

Central Dogma: DNA Extraction

After reviewing the Unit 4 final exams, it was evident students need additional practice writing scientific procedures.  Today, students were tasked with watching a short video of DNA extraction from a strawberry, writing a procedure for the experiment, and then working with their table partner to complete the experiment. By having to follow their own procedure, the concept of writing a procedure in enough detail for someone else to follow it was reinforced.  Students will use the procedures they wrote today to help them write a related procedure tomorrow.  Click here for today’s lesson and review the strawberry DNA extraction video below.

Central Dogma: DNA base pairing

With all of the HHS science teaching staff participating in a Studio Day, students were tasked with completing a DNA base pairing worksheet with guidance from a substitute teacher.   Students learned that in complementary DNA strands, A pairs with T and C pairs with G.  When RNA is transcribed from DNA, the rules are the same with one exception: mRNA uses U instead of T, so in a DNA:RNA pairing, the A in DNA pairs with U in RNA.  Students went on to learn about codons (adjacent sets of 3 RNA bases) and learned how codons code for amino acids.  Students learned how to write the 3-letter and 1-letter amino acid abbreviations, and solved the amino acid structure from a DNA strand, as well as solved a DNA strand from a short amino acid sequence.

Central Dogma: Introduction to DNA

We began class with a new seating chart.  Students organized themselves by birth month and were seated in pairs.  Students were reminded how important it is to make new friends and engage with new people to learn new ideas and ways of approaching a scientific challenge.

After the seating chart, students were provided with a timeline for making up work from the last two weeks of Unit 4.  All late work and revisions are due by this Friday.  Students were also reminded to check in on the class website daily and to monitor the new Twitter feed for interesting science articles.

Next, we launched in to Unit 5: Central Dogma.  Students were asked to write down everything they know about DNA and then shared their knowledge with their new table partner.  Students were encouraged to use the agree/disagree structured partner talk strategy.  Student pairs then shared one piece of information about DNA that they discussed by writing it on a class white board.  An example of the information from one class is given below.

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Finally, students received a few slides of instruction regarding Central Dogma vocabulary before we watched the first 16 minutes of Cosmos: Episode 2.  The last slide of the lesson lists the questions students answered while watching the video.