Strome, Susan
Although we have been working on the elements of this list for this last week and
half, I feel like my final list needs much additional reflection and bringing
together parts of this program. I need some time to let this 2 weeks of ideas
percolate and to let the “best” possibilities for my course rise to the top of my big
piles of possibilities. I am having the most trouble with evaluation – CATs and
exam questions – I need to think long and hard about those. My “lesson” will
extend over several weeks, as we revisit and revisualize chromosomes in several
different situations. I will next teach L311 Genetics in spring of 2004, and my
final assessment will be after RFLPs, so probably March.
Step 1: Define a Bottleneck
Many genetics students are unable to effectively manipulate chromosomes during
mitosis and meiosis and in crosses. Students are confused about terminology
(e.g., “sister chromatid”, “homolog” and “allele”), the changing landscape (i.e. the
different chromosomal situation within a cell at different stages of the cell cycle
and between different cell types), and how to represent chromosomes and genes
on chromosomes.
Step 2: Define the Basic Learning Tasks
As an “expert” I visualize and represent chromosomes in very specific and useful
ways. I represent them as lines (not X’s) – each line represents a long thread of
DNA and that thread contains many genes. I initially think about chromosomes
in the G1 phase of the cell cycle, when I don’t have to worry about sister
chromatids – the distinction between homologs and different chromosomes is
easy in G1. When I do mitosis, meiosis, and crosses, I know to ignore all of the
chromosomes and genes that are not relevant to the task – in the simplest case I
focus only on the 2 homologs and the 2 versions of a gene present on those 2
homologs, and I ignore all the other chromosomes and genes. This ignoring
business is critical. If I am doing a cross, I never formally move through all the
steps of meiosis (I ignore those) – instead I move straight to the end products of
meiosis (gametes) and work with the single homolog present in each gamete. If I
need to think about the mechanics of meiosis, then working with my trimmed
down set of only 2 homologous chromosomes, I make exact duplicates of each –
the 2 sister chromatids made from 1 homolog are identical to each other – and
head them into meiosis (another bottleneck, to be tackled).
Step 3: Model these Tasks Explicitly
I will help my students visualize the chromosomal composition of organisms, and
the similarities and differences between sister chromatids, homologs, and
different chromosomes by using colored pipe cleaners and beads and by
complementing this with drawn representations that we can use throughout the
semester. I plan to start with G1 cells and the chromosomes I used in my lesson
to FLP. I think a critical component is ignoring most of the pipe cleaners and
most of the beads, and focusing only on the “relevant” ones.
Step 3 1/2.: Motivate the students
One motivator will be making clear to them early on all the different ways in
which genetics is relevant to our lives – it tells us about reproduction, birth
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defects, diseases, cancer, aging, gene and cell therapies, antibiotics, etc. Another
motivator will be doing tasks that are interesting to them and raise questions and
ethical dilemmas (cystic fibrosis). Another motivator will be having fun with
some goofy examples.
Step 4: Create Occasions for Students to Practice These Steps and Receive
Feedback
I will use pipe cleaners and ask for chromosome drawings during several
different small group activities that focus on different concepts and that build in
complexity. I like the idea of starting with a simple genetic cross and asking the
students to bring different parents (chromosomes/genes) together and think
about the possible combinations of chromosomes/genes in the offspring – cystic
fibrosis exercise but without a child. I want the lesson to be simple enough that
everyone focuses on the basic visualization exercise and “gets it”, but I need to
add an element of complexity that will challenge those for whom this is easy and
natural. I am still thinking about how best to bring the small-group activity back
to the whole group for discussion, and about CATs that will work for this.
Step 5: Assess how well students are mastering these learning tasks
I will focus tonight on problem set and exam questions that focus on my
bottleneck and that aim at different levels of Bloom’s Taxonomy.
Step 6: Share what you have learned about your students’ learning
I’m not sure what this step is about – share with the students or with other
instructors?
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