BLG 151 Chapter Notes - Chapter 1: Recombinant Dna, Acronym, Hyperlink
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From the lab kit, find the piece of colored fabric and pieces of colored foam. Open the fabric and spread it out on a flat surface. Using the paper hole punch and punch template from the lab kit, punch out 30 dots from each of the 10 colors of foam.
Each colored circle represents an individual rabbit of the type known as Rabbiticus hopquickus. A starting population of 100 rabbits that live in a meadow will be used in this experiment. The experimenter will assume the role of a coyote of the type known as Coyotus predacious. Coyotus predacious like nothing better than to feast on a choice specimen of Rabbiticus hopquickus. Normally, the only death in the population of Rabbiticus is due to predation by Coyotus predacious. The piece of fabric simulates a meadow on the island of Darwinia, the only island on which both Rabbiticus hopquickus and Coyotus predacious have been seen. Variations of individuals are characteristic of organisms of the same species.
Begin the simulation by placing 100 rabbits (10 dots each of 10 different colored circles) into a cup. Mix them up by shaking or inverting the container. Scatter the rabbits randomly over the surface of meadow (the fabric).
Begin the simulation. Don’t stare at the distribution of the dots on the fabric, but rather look away until ready to begin. Begin by turning toward the fabric and use the forceps to pick up the first dot (rabbit) that stands out. The rabbits (dots) picked up are those that are easiest to see. After a rabbit is selected, immediately look away from the fabric. The captured rabbits should be brought to the coyote den (the cup). Repeat this procedure until a total of 75 rabbits have been captured, remembering to look away from the meadow after each capture. Twenty-five rabbits should remain in the meadow. The object is to capture the rabbit that is first observed when looking at the fabric.
Gently shake the meadow and collect the 25 surviving rabbits. These are the rabbits that will produce the second generation. Divide them into piles according to color. Rabbiticus hopquickus is noted to have both male and female reproductive organs in the same individual and thus can fertilize itself. Each surviving rabbit will now reproduce. For each dot, use the hole punch to cut out an additional three circles (baby rabbits) that are the same color as the parent. Record the number of rabbits of each color in a chart similar to the chart provided, below. Put all of the rabbits (100 total) into the plastic cup, shake them, and disperse them at random on the meadow.
Simulate two more generations of Rabbiticus by repeating Steps 4 and 5 two more times. Keep track of the numbers of each kind of rabbit by making a chart like the one below. The only difference is that a total of 10 colors should be recorded in the chart.
| Color | Original Population | 1st Generation | 2nd Generation | 3rd Generation |
|---|---|---|---|---|
| green | 10 | |||
| purple | 10 | |||
| light blue | 10 | |||
| red | 10 | |||
When finished with the last round of predation and reproduction, count the color and number of each of the 25 surviving rabbits. Then multiply each number by four to get back to 100 rabbits.
Assume surviving rabbits are all yellow.
Could this population adapt to a new environment where the predominant color is purple? (2 points)
Why or why not? (3 points)
Why did the results come out the way they did? Explain why all of the colors of rabbits did not end up with the same population size. The explanation here should demonstrate an understanding of natural selection.
Experiment 1 Fermentation by Yeast Experiment Inventory Labware (4) 250 mL Beakers (1) 100 mL Graduated Cylinder (1) Test Tube Rack (5) Fermentation Tubes = (10) Test Tubes (5 plastic and 5 glass; see Figure 4) (1) Measuring Spoon (4) Pipettes (1) Ruler Note: You must provide the materials listed in *red. EXPERIMENT 1: FERMENTATION BY YEAST Yeast cells produce ethanol, C2 H6 O, and carbon dioxide, CO2 , during alcoholic fermentation. In this experiment, you will measure the production of CO2 to determine the rate of fermentation in the presence of different carbohydrates with fermentation tubes. Note: Regular table sugar is sucrose, a disaccharide, which is made up of glucose and fructose. Glucose is a monosaccharide. Figure 4: Fermentation tubes. Note how the smaller, plastic test tube is inverted into the larger glass tube. You will create five fermentation tubes in this experiment. PROCEDURE 1. In this experiment, you will mix yeast with sugar, Equal®, and Splenda®. Before you begin, develop a hypothesis predicting what will happen when the sugar/sweeteners are mixed with yeast. Will fermentation occur? Why or why not? Record your hypothesis in the post-lab questions. 2. Use the permanent marker to label three 250 mL beakers as Equal®, Splenda®, and Sugar. 3. Empty the Equal®, Splenda®, and Sugar packets into the corresponding beakers. 4. Fill the Equal® and Splenda® beakers to the 100 mL mark with warm tap water. 5. Fill the Sugar beaker to the 200 mL mark with warm tap water. 6. Mix each beaker thoroughly by pipetting the solution up and down several times. Use a new pipette to mix each solution. Each beaker now contains a 1% solution. Set these aside for later use. 7. Completely fill one of the smaller plastic tubes with tap water and invert the larger glass tube over it. Push the small tube up into the larger tube until the top connects with the bottom of the inverted tube. Invert the fermentation tube (Figure 4) so that the larger tube is upright (there should be a small bubble at the top of the internal tube). Note: Repeat Step 7 several times as practice. Strive for the smallest bubble possible. When you feel comfortable with this technique, empty the test tube(s) and proceed to Step 8. CAUTION: Do not try to force the plastic test tube into the glass test tube. This might cause your glass test tube to break, causing you injury. If your plastic test tubes do not fit easily, please call eScience Labs for replacement glass tubes. If you are able to set up at least two fermentation tubes, continue with the experiment, but know that you will have to perform steps 12-15 in multiple steps. 8. Use the permanent marker to label the fourth 250 mL beaker as Yeast. 9. Fill this beaker with 175 mL of warm tap water. It should be between 30 and 40o C (warm to the touch). 10.Open the yeast package, and use the measuring spoon to measure and pour 1 tsp. yeast into the beaker. Pipette the solution up and down until all of the yeast is mixed homogenously into the solution. Note: Make sure the yeast solution remains homogenous before each test tube is filled in the proceeding steps. The yeast density is fairly high, and the yeast may settle to the bottom of the beaker if it rests for an extended period of time. 11. Use the permanent marker to label the big glass and small plastic test tubes as 1, 2, 3, 4, and 5. 12.Use the 100 mL graduated cylinder to measure and pour 15 mL of the following solutions into the corresponding small plastic test tubes: Tube 1: 1% Glucose Solution Tube 2: 1% Sucrose Solution Tube 3: 1% Equal® Solution Tube 4: 1% Splenda® Solution Tube 5: 1% Sugar Solution Note: Thoroughly rinse the graduated cylinder between each measurement. 13.Fill the remaining volume in each small tube to the top with the yeast solution. 14.Slide the corresponding larger tube over the small tube and invert it as practiced in Step 7. This will mix the yeast and sugar/sweetener solutions. 15.Place the fermentation tubes in the test tube rack, and use a ruler to measure (in millimeters) the initial air space in the rounded bottom of the internal tube. Record these values in the Table 1. 16.Allow the test tubes to sit in a warm place (approximately 30 °C) for two hours. Placement suggestions include: a sunny window sill, atop (not in!) a warm oven heated to approximately 85 °C (185 °F on an oven setting), or under a very bright (warm) light. 17.At the end of the fermentation period, use your ruler to measure (in millimeters) the final gas height (total air space) in each tube. Record this data in Table 1. 18.Calculate the difference between the initial and final gas height in each tube. Record this data in Table 1.
EXPERIMENT 1: FERMENTATION BY YEAST
Result Tables
Table 1: Yeast Fermentation Data
| Tube | Initial Gas Height (mm) | Final Gas Height (mm) | Net Change (mm) |
|---|---|---|---|
| 1 | |||
| 2 | |||
| 3 | |||
| 4 | |||
| 5 |
Post-Lab Questions
Include your hypothesis from Step 1 here. Be sure to include at least one piece of scientific reasoning in your hypothesis to support your predictions.
Did you notice a difference in the rate of respiration between the various sugars? Did the artificial sugar provide a good starting material for fermentation?
Was anaerobic fermentation occurring? How do you know (use scientific reasoning)?
If you observed respiration, identify the gas that was produced. Suggest two methods you could use for positively identifying this gas.
Hypothesize why some of the sugar or sweetener solutions were not metabolized, while others were. Research the chemical formula of Equal® and Splenda® and explain how it would affect yeast respiration.
How do the results of this experiment relate to the role yeast plays in baking?
What would you expect to see if the yeast cell metabolism slowed down? How could this be done?
Indicate sources of error and suggest improvement (for example, what types of controls could be added?).