Teacher's+Notes+for+Genetics+Lab+Sequence

=I. Activity: Probability and Coin Flips=

Pre-Lab Discussion:
 * Introduce this activity as an opportunity to add an important tool to our mathematical toolkit, then explain the goal: to look for patterns in the outcome when a coin is tossed a large number of times, and then to do the same when a //pair// of coins is tossed a large number of times.
 * Then give them the handout.

Performance Notes:
 * As students work on the analysis questions, circulate and ask questions to help them with the quantitative analysis. By having them articulate the qualitative patterns that they note and the "expected" outcomes, lead them to calculate a percent difference, thereby enabling a quantitative comparison of the sample sizes.

Post-Lab Discussion:
 * Lead students to a clear articulation of the answers to the analysis questions, and particularly to the observed ratios and the need for a large sample size to observe those ratios

=II. Lab: Dihybrid cross with corn=

Pre-Lab Discussion:
 * Show students demonstration pallet with the three generations of corn, and ask for observations. These will hopefully include:
 * Different colors
 * Different shapes - round v. wrinkled.
 * Light and wrinkles both disappear in the 2nd generation, then come back.
 * The traits are mixed in the 3rd generation, including yellow round and black wrinkled.
 * In an attempt to model what is going on, lead students to count the number of each type of kernel in the 3rd generation. Elicit ideas on how to organize the data table, and agree on a format as a class before proceeding.

Performance Notes:
 * As students work on their analysis, prompt them to explore one trait at a time for simplicity. They should notice a 3:1 pattern. This is the tricky part of the discussion, and the teacher will have to seed ideas with the groups as they try to model this pattern. They may at first be surprised not to see a 1:1 pattern; ask them why this surprises them. You can then, when the coins are mentioned, lead them to consider the other coin pattern, which also has a total of 4 (1 + 2 + 1). Some may come to see that if you just look at how many combinations had a head, the coin also yielded a 3:1 ratio, and this can lead to a model wherein each kernel contains two coins for the color trait. The disappearance of yellow in the 2nd generation may help lead them. Some groups may get to this while doing their analysis, or it may only be fully developed in class discussion.

Post-Lab Discussion:
 * Here, students can be lead to put all the pieces together, hopefully due to some good seeding of ideas in the analysis phase, but if not, through some good questioning. This "two coins" in a corn model combined with the idea of dominance will be seen to explain the data for each trait taken separately. Then, students can discuss how to model the combination of traits, can initially consider (and reject) a model where each coin codes for two traits (wouldn't match the data), and come to a 4-coin model. They can then be led to go back and do a set of 4-coin flips to see if the results match the combined data.

Lab extension / development of complete model:
 * Discussion of why there are two coins, bringing in prior knowledge; development of the detailed chromosome model; introduction of terminology.

Deployment activities:
 * Groups practice punnet square-type problems and discuss them using whiteboards. Instructor asks ample "why did you do that?" and "how do you know?" questions to bring the students to full understanding before they are asked to deploy the model individually.