Compose answers to the questions below and save the file as a backup copy in the event that a technical problem is encountered while attempting to submit the assignment. Make sure to run a spell check.

You will be submitting your answers to the lab assignment in two parts. The first part of the lab assignment consists of the laboratory exercise questions. The second part of the lab assignment is the application question. The first textbox on the submission page corresponds to the first part of the lab. Be sure to paste the laboratory exercise questions, with your answers, into this textbox. The second textbox on the submission page will be for your response to the application question.

LABORATORY EXERCISE QUESTIONS

~~1. What is an allele? (1 point)

~~2. Give an example of a genetic trait and two allele phenotypes for the gene that determines the trait. (3 points)

a. Genetic Trait

b. Allele phenotype #1

c. Allele phenotype #2

~~3. Compare and contrast the terms phenotype and genotype. (4 points)

~~4. List the allele combinations (gamete possibilities) that can be formed by an individual with the following genotype: AABB (1 point)

~~5. List the different allele combinations (gamete possibilities) that can be formed by an individual with the following genotype: AaBb. (4 points)

a.

b.

c.

d.

~~6. Given: P = purple flowers and p = white flowers and P is dominant over p.

a. What is the phenotypic ratio of offspring from a cross between Pp x pp? (2 points)

b. In a population with 160 individuals how many will be homozygous? (2 points)

c. In that same population, how many will be purple? (2 points)

~~7.

a. Which of Mendel’s laws is illustrated in a dihybrid cross? (1 point)

b. What does this law state? (1 point)

~~8. A horticulturist has a purple plant and a white plant. The horticulturist knows that purple is dominant over white. When they are bred, all of the resulting offspring are purple. What is the most likely genotype of the parent or original purple plant? (2 points)

~~9. A horticulturist runs a test cross with an offspring (F1 generation) purple plant from Question 8. The phenotypic frequencies of the resulting offspring are 50% white and 50% purple. What is the true genotype of this offspring (F1 generation) purple plant? (2 points)

~~10. What is the probability of a cross resulting in white offspring when two heterozygous purple pea plants (e.g. Pp x Pp) are bred? What is the genotype for this offspring? (4 points)

~~11. Compare the ratios calculated in Exercises 5 and 6 (coin toss activity) to Mendel’s ratios. Were they close? Pose a possible explanation for why the ratios may not be exactly the same. (4 points)

~~12. Refer to the data on the corn kernel color ratio from Part II of the lab.

a. What was the phenotypic ratio from Step 1? (2 points)

b. What was the phenotypic ratio from Step 2? (2 points)

c. What was the phenotypic ratio from Step 3? (Remember there were four possible types for this part of the lab.) (2 points)

d. Explain why your numbers did not come out exactly. (2 points)

~~13. Recall from the background information that purple kernels are dominant and yellow kernels are recessive. The second ear of corn was the result of crossing two heterozygous ears of corn male purple (Pp x Pp). This is represented by the Punnett square below. Complete the Punnett square by writing the correct letters that correspond to each number indicated in the table. (4 points)

1.

2.

3.

4.

~~14. Once the Punnett square for Question 13 is complete, calculate the ratio of purple and yellow kernels (recall that if the dominant trait is present, it will be expressed).

h. What is the ratio of purple to yellow kernels based on the Punnett square? (2 points)

h. How did this compare to the ratio obtained from counting the corn kernels for ear number two in part II of the lab? (2 points)

~~15. Recall from the background information that purple kernels are dominant and yellow kernels are recessive. Also recall that smooth kernels are dominant and wrinkled kernels are recessive. The third corn ear was the result of crossing a male ear of corn with the following gametes: PpSs, with a female ear of corn with the same gametes: PpSs. This is represented by the Punnett square, below. Complete the Punnett square by writing the correct letters that correspond to each number indicated in the table (for example, PPSS or ppss). (8 points)

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

13.

14.

15.

16.

~~16. Once the Punnett square for Question 15 is complete, calculate the ratio of corn kernel varieties (recall that if the dominant trait is present, it will be expressed).

a. What is the ratio of kernels based on the Punnett square? (2 points)

b. How does this compare to the ratio obtained from counting the corn kernels? (2 points)

~~17. What are the genotypic and phenotypic ratios for kernel color and kernel texture for a dihybrid cross between PpSS x Ppss? (4 points)

c. genotypic ratio

d. phenotypic ratio

~~18. Using the results from the Punnett Square in Question 15, answer the following question: In a population of 240 corn kernels, how many will have smooth kernel texture? (2 points)

~~19. In a flower garden, a horticulturist is growing purple and white pansies. The horticulturist notices that a new pansy has sprouted. When it finally flowers, the pansy is lavender. Explain how this happened. (4 points)

~~20. With a botanist’s help, an individual decides to cross the lavender pansy with the white pansy. Will this result in any purple pansies? Explain. (4 points)

~~21. State an industrial concern/importance for knowing the genetic makeup of an organism. Explain why it is important in your example. (5 points)

APPLICATION QUESTION

~~22. (Application) How might the information gained from this lab pertaining to genetics be useful to you, or how can you apply this knowledge to your everyday life as a non-scientist? The application will be graded according to the rubric below. (20 points)

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BIOL 102: Lab 7

Yeast Fermentation

PRE-LAB ASSIGNMENT:

Students are expected to read pages 1-2 before coming to the lab to complete the experiments.

Print this entire lab packet and bring it to the laboratory.

Please provide a FULL lab report for this experiment following the “Lab Report Guidelines”.

Please note that this lab report WILL include a HYPOTHESIS.

Objectives:

· Observe yeast fermentation

· Determine the optimum conditions for yeast fermentation

Background:

All fungi are eukaryotes. Although they vary in size and shape, fungi share key characteristics including their way of obtaining nutrients for growth and energy. Fungi are heterotrophs and they depend on preformed carbon molecules produced by other organisms. However, fungi do not ingest food and then digest it using enzymes; instead they invade -think of a moldy piece of bread-a food source and secrete digestive enzymes onto it. The digestion occurs outside the body. When the polymers are broken down into monomers, the fungi absorb the predigested food into its body.

Yeast are microscopic, unicellular organisms in the Kingdom Fungi. Like other fungi, yeast are incapable of making their own food, but like any other organism, need food for energy. They rely on carbohydrates (usually sugars) found in their environment to provide them with this energy so that they can grow and reproduce. There are many species of yeast, and each has a particular food source.

Regardless of the food source, yeast perform fermentation which does not utilize oxygen. In fermentation, the only energy extraction pathway is glycolysis, with one or two extra reactions tacked on at the end, but no electron transport chain. Therefore, only 2 ATPs are formed per glucose.

Fermentation and cellular respiration begin the same way, with glycolysis. In fermentation, however, the pyruvate made in glycolysis is not completely oxidized because it does not continue through the citric acid cycle and the electron transport chain does not run. Because the electron transport chain is not functional, the NADH cannot drop its electrons off to the electron transport chain, and thus very few ATP molecules are synthesized because the ATP synthase is not running.

Based on the end products, fermentation can be of two types: ALCOHOLIC fermentation (the subject of this lab) and LACTIC ACID fermentation.

Regardless of the type of fermentation, the purpose of the extra reactions in fermentation, is to regenerate (recycle) the electron carrier NAD+ from the NADH produced in glycolysis. The extra reactions accomplish this by letting NADH drop its electrons off with an organic molecule such as acetaldehyde to produce ethanol (alcoholic fermentation), or pyruvate to produce lactic acid (lactic acid fermentation). This “drop-off” of electrons allows glycolysis to keep running by ensuring a steady supply of NAD+.

Going from pyruvate to ethanol is a two-step process. In the first step, a carboxyl group is removed from pyruvate and released as carbon dioxide, producing a two-carbon molecule called acetaldehyde. In the second step, NADH passes its electrons to acetaldehyde, regenerating NAD+ and forming ethanol.

Yeast breaks down glucose into ethanol, 2 carbon dioxide molecules, and 2 ATP molecules. The formula for the yeast fermentation reaction is:

Reactant Products

C6H12O6 >>>>>>> 2CH3CH2OH + 2CO2 + 2 ATP molecules

For the yeast cell, this chemical reaction is necessary to produce the energy for life. The ethanol and the carbon dioxide are waste products. It is these waste products that we take advantage of: we use the ethanol in alcoholic beverages and the carbon dioxide makes bread rise when baking.

Alcoholic fermentation, can be observed and measured by using the amount of carbon dioxide gas that is produced from the breakdown of glucose. In this exercise, you will observe alcoholic fermentation by yeast. To do so you will add the same amounts of yeast and water to different amounts of sugar in Erlenmeyer flasks and cap them with a balloon to see how much carbon dioxide gas is produced. You will also use water at two different temperatures and determine how much carbon dioxide is produced. The more fermentation that occurs, the more carbon dioxide will be produced, and the more the balloon will expand.

Information adapted from:

Solomon, Eldra P. et al. Biology. 10th ed. Cengage, 2015.

https://www.khanacademy.org/science/biology/cellular-respiration-and-fermentation

LAB DATASHEET

Determine the optimum conditions for yeast fermentation.

Think Scientifically:

Please explain your rationale to which flask or test variable will produce the most CO2. Look at the various bottles below and state whether bottle A-F will produce the most CO2 and explain why.

Materials:

Sugar

Dry yeast

Warm water

Ice cold water

Balance scale

Measuring spoons

100 mL Graduated Cylinder

6 Erlenmeyer flasks

6 Rubber bands

6 Balloons

Ruler

Procedure:

1. Obtain 6 labeled Erlenmeyer flasks.

2. Fill each flask accordingly:

· Bottle A – 5 mL sugar, 3 grams of dry yeast

· Bottle B – 10 mL sugar, 3 grams of dry yeast

· Bottle C – 15 mL sugar, 3 grams of dry yeast

· Bottle D – 5 mL sugar, 3 grams of dry yeast

· Bottle E – 3 grams of dry yeast

· Bottle F – 15 mL sugar

3. Fill all flasks except D with 100 mL of warm water. Fill flask D with 100 mL of ice cold water.

4. Place a balloon over the top of each flask and tighten it with a rubber band.

5. Swirl flask to mix contents. Wait 20-30 minutes.

6. Record observations in Table 1.

7. Measure the width and height of the balloon (from the top of the flask to the top of the balloon) with a ruler, and record it in Table 1.

8. Graph the Sugar Quantity vs. Balloon Height in an X-Y Scatterplot. Insert DIGITAL scatterplot only. Written graphs and/or pictures of written graphs will not be accepted.

Conclusion:

Be sure to address the following:

· How did your original rationale compare to the data collected? If your rationale was incorrect, why do you think it did not produce the most CO2?

· Describe what happened in this reaction using the following terms: yeast, warm water, cold water, sugar, anaerobic respiration, and carbon dioxide.

· Compare what happened to each of the balloons for flasks A through F. Which flask had the most CO2 production? Least? How do you know? Be sure to describe WHY!

· There were four experimental flasks and two control flasks in this exercise. Which flasks were the experimental and which were the control flasks? Explain how each determination was made.

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