Unit 7 "Alternate" Plan

The main plan for Unit 7 calls for 45+ days of growing pea plants prior to beginning the heredity unit.  That really isn't feasible for me at my school... although the real reason this idea was thrown out the window is because I didn't carefully read the Unit 7 lesson plan until about three weeks ago.  Oops.

Luckily, they give an alternate lesson plan for those of us without resources (or in my case, time) to execute the fast pea plant experiment.  It starts off with a simulation entitled "Potato Head Genetics."

Stock Mr. Potato Head photo stolen off the internet

We kicked off this activity on the Monday and Tuesday before Thanksgiving break.  Not exactly the best time to be starting something new, but we are pressed for time before the end of the semester.

In a perfect world, I would have 34 Mr. & Mrs. Potato Heads with a variety of different color "parts" to distribute to my students.  While they are only about $5 a piece, I wasn't about to spend nearly $200 of my own money on Potato Heads.  At the same time, I definitely wasn't going to walk into my department head's room with a P.O. for 34 Potato Heads, either.  So... back to the drawing board.  Quite literally in this case.  I bought one Mr. Potato Head from Walmart as a "model," but then had students draw their own.

The general idea of this lesson plan is we have to repopulate the Potato Head species by using a gamete bank to make test tube Potato Heads, then interbreed them to produce more offspring.  The goal is to introduce the concept of punnett squares, dominant/recessive alleles, incomplete dominance, co-dominance, multiple alleles, dihybrid crosses, etc

The lesson plan kept talking about this "gamete bank."  I was incredibly confused about how I was supposed to set this gamete bank up.  At a loss, I ended up spending tons of time making sets of popsicle sticks for each allele. Students randomly choose sticks out of baggies to determine the genotype of the test tube potato.  At the end of the day Tuesday, I realized I somehow missed this file in the lesson plans:

Gametes for the gamete bank.  These would have made my life easier.

As far as creating test tube potato zygotes, I tried doing it a few different ways in my classes.  In a smaller class, I split the room into boys and girls (since we had about equal numbers).  They randomly drew popsicle sticks to determine the genes carried by the male gamete and the female gamete.  Then we joined them together and drew the new individual.  I then reviewed the terms "phenotype," "genotype," and "allele" from unit 3 and we introduced new terms of "dominant" and "recessive."  We then discussed multiple alleles, incomplete dominance, co-dominance, homozygous, and heterozygous.

In my larger classes, I tried to have each lab group draw from the baggies to create a gamete, then join with a different group to make an offspring:

The product of fertilization

Next, in an attempt to introduce punnett squares and probability, students were to trace a gene through meiosis.  This is a great activity to show teachers just how well your students didn't learn meiosis.  Granted, we had to rush through Unit 6, but it became painfully apparent that my students didn't understand meiosis at all.  Sure, they could give rudimentary drawings and explanations of the steps, tell me about the 4 haploid gametes, tell me about crossing over... but attempting to trace a gene through meiosis proved impossible for most groups.  And quite frankly, there wasn't enough time to make them claw their ways to understanding.  As a result, punnett squares got put on hold and we jumped ahead to "mating" our potatos.

We did this activity on the Tuesday before Thanksgiving break, so as you can imagine, the students were off the wall.  "Do you realize you are the ONLY teacher in the ENTIRE school making us do work today?"  Haha, right...

Ideally, for mating, all students were supposed to start with similar genotypes from the gamete crosses.  Of course, since that went dreadfully, I ended up making quick "genotype" cards to distribute.   I did use the include data sheets, but I modified the activity again-- instead of doing multiple generations, students had to find a mate and create two offspring, all while listening to the sweet, sweet tunes of Billy Paul:

When we come back to class tomorrow, we're going to kick off punnett squares by discussing why our children don't look exactly like the parents, and then asking how could we predict the likelihood that a trait will be passed on...

I feel like I'm in constant "damage control" mode lately-- lessons keep not going as intended, and I have to figure out how to make something out of them the next day... sigh.  I'm really curious to see my students end of course exam scores after this semester... have they truly gotten anything out of this semester?  It's hard to tell some days...