Meiosis

Following chromosomal DNA movement

Part 1 – Meiotic Division Beads Diagram WITHOUT Crossing Over (each photo is worth 2 points for a total of 18 points)

Take pictures of your beads for each phase of meiosis I and II without crossing over. Include notes with your name, date and meiotic stage on index cards in the pictures. 

StageColored Sketch or Photos of Beads
Prophase I

-continued next page-

StageColored Sketch or Photos of Beads
Metaphase I
Anaphase I
Telophase I
Prophase II
Metaphase II

-continued-

StageColored Sketch of Beads
Anaphase II
Telophase II
Cytokinesis

Part 2 – Meiotic Division Beads Diagram WITH Crossing Over (each photo is worth 2 points for a total of 18 points)

Take pictures of your beads for each phase of meiosis I and II with crossing over. Include notes with your name, date and meiotic stage on index cards in the pictures. 

StageColored Sketch or Photos of Beads
Prophase I

-continued next page-

StageColored Sketch or Photos of Beads
Metaphase I
Anaphase I
Telophase I
Prophase II
Metaphase II

-continued-

StageColored Sketch of Beads
Anaphase II
Telophase II
Cytokinesis

Questions

1. What is the ploidy of the DNA at the end of meiosis I? What about at the end of meiosis II? (each part of question is worth 2 points, for a total of 4 points)

2. How are meiosis I and meiosis II different? (worth 2 points)

3. Why do you use non-sister chromatids to demonstrate crossing over? (worth 2 points)

4. What combinations of alleles could result from a crossover between BD and bd chromosomes? (worth 2 points)

5. How many chromosomes were present when meiosis I started? (worth 2 points)

6. How many nuclei are present at the end of meiosis II? How many chromosomes are in each? (each part worth 2 points for a total of 4 points)

7. Identify two ways that meiosis contributes to genetic recombination? (each part worth 1 point for a total of 2 points)

8. Why is it necessary to reduce the number of chromosomes in gametes, but not in other cells? (worth 2 points)

9. Blue whales have 44 chromosomes in every somatic cell. Complete the table below by entering in the final column the number of chromosomes you would expect to find in each of the indicated cells: (each cell in table is worth 1 points, for a total of 4 points)

Cell Type# Chromosomes
Sperm cell
Egg cell
Daughter cell from meiosis I
Daughter cell from meiosis II

10. Research and identify a disease that is caused by chromosomal mutations. Briefly describe the diseaseWhen does the mutation occur? What chromosome(s) is/are affected? What are the consequences? (question has 4 parts, each part of question is worth 2 points, for a total of 8 points)

11. Diagram what would happen if sexual reproduction took place for four generations using diploid (2n) cells? (worth 3 points)

-continued-

Experiment 2: The Importance of Cell Cycle Control (29 points)

Data Table (each abnormality worth 1 point, each drawing worth 2 points, for total of 15 points)

AbnormalityDrawing of Abnormality
1.
2.
3.
4.
5.

Questions

1. Record your hypothesis from Step 1 in the Procedure section here. (worth 2 points)

2. What do your results indicate about cell cycle control? (worth 2 points)

3. Suppose a person developed a mutation in a somatic cell which diminishes the performance of the body’s natural cell cycle control proteins. This mutation resulted in cancer, but was effectively treated with a cocktail of cancer-fighting techniques. Is it possible for this person’s future children to inherit this cancer-causing mutation? Be specific when you explain why or why not. (worth 3 points)

4. Why do cells which lack cell cycle control exhibit karyotypes which look physically different than cells with normal cell cycle. (worth 3 points)

5. What are HeLa cells? Why are HeLa cells appropriate for this experiment? (each part worth 2 points, for a total of 4 points)

TYPE YOUR FULL NAME:

Cell Structure and Function

1. Diagram Labelling: Identify each of the labeled structures in the following slide image of an onion root tip (1000X):

(2 point for each = 8 points)

A
B
C
D

2. What is the difference between the rough and smooth endoplasmic reticulum? (2 points)

3. (a) Would an animal cell be able to survive without mitochondria? (1.5 points) (b) Why or why not? (3.5 points)

a
b

4. What could you determine about a specimen if you observed a slide image showing the specimen with a cell wall, but no nucleus or mitochondria? (5 points)

5. Hypothesize why parts of a plant, such as the leaves, are green, but other parts, such as the roots, are not. Use scientific reasoning to support your hypothesis. (5 points)

Experiment 2: Osmosis – Direction and Concentration Gradients (75 points)

Data Tables and Post-Lab Assessment

Table 3: Sucrose Concentration vs. Tubing Permeability

(each cell is worth 1.5 points = 30 points for the table)

Band Color% Sucrose in Beaker% Sucrose in BagInitial Volume (mL)Final Volume (mL)Net Displacement (mL)
Yellow
Red
Blue
Green

Take a picture of your results. Include a note with your name and date on an index card in the picture. Insert picture here (3 points):

Hypothesis: (2 points)

Post-Lab Questions

1. For each of the tubing pieces, identify whether the solution inside was hypotonic, hypertonic, or isotonic in comparison to the beaker solution in which it was placed, by completing the following table: (2.5 points per cell = 10 points)

Solution in tubing with ____ band color….…was hypertonic, hypotonic, or isotonic (select one)……in comparison to…
Yellow…beaker solution in which it was placed.
Red
Blue
Green

2. (a) Which tubing increased the most in volume? (1.5 points) (b) Explain why this happened. (3.5 points)

a
b

3. What do the results of this experiment this tell you about the relative tonicity between the contents of the tubing and the solution in the beaker? (5 points)

4. What would happen if the tubing with the yellow band was placed in a beaker of distilled water? (5 points)

5. How are excess salts that accumulate in cells transferred to the blood stream so they can be removed from the body? Be sure to explain how this process works in terms of tonicity. (5 points)

6. If you wanted water to flow out of a tubing piece filled with a 50% solution, what would the minimum concentration of the beaker solution need to be? Explain your answer using scientific evidence. (5 points)

7. (a) How is this experiment similar to the way a cell membrane works in the body? (2.5 points) (b) How is it different? (2.5 points) Be specific with your response.

a
b

TYPE YOUR FULL NAME:

D

A

B

C

Enzymes In Food

Data Tables and Post-Lab Assessment

Table 1: Substance vs. Starch Presence

(1 point each cell = 13 points)

Substance NameResulting ColorPresence of Starch?(yes or no)
Positive Control:Ginger Root
Negative Control:Student Selects
Food Product:Student Selects
Food Product:Student Selects
Required:Saliva

Take a picture of your results. Include a note with your name and date on an index card in the picture. Insert picture here (3 points):

Post-Lab Questions

1. a) What were your controls for this experiment? b) What did they demonstrate? c) Why was saliva included in this experiment? (2 points each part = 6 points)

a
b
c

2. a) What is the function of amylase? b) What does amylase do to starch? (2 points each part = 4 points)

a
b

3. a) Which of the foods that you tested contained amylase? b) Which did not? c) What experimental evidence supports your claim? (2 points each part = 6 points)

a
b
c

4. Saliva does not contain amylase until babies are two months old. How could this affect an infant’s digestive requirements? (1 points)

5. There is another digestive enzyme (other than salivary amylase) that is secreted by the salivary glands. a) Research to determine what this enzyme is called. b) What substrate does it act on? c) Where in the body does it become activated, and why? (2 points each part = 6 points)

a
b
c

6. Digestive enzymes in the gut include proteases, which digest proteins. a) Why don’t these enzymes digest the stomach and small intestine, which are partially composed of protein? (2 points)

Experiment 2: Effect of Temperature on Enzyme Activity (59 points)

Data Tables and Post-Lab Assessment

Table 2: Balloon Circumference vs. Temperature

(1.5 point each cell = 15 points)

TubeTemperature (°C)Balloon Circumference (Uninflated; cm) (same value applies to all tubes)Final Balloon Circumference (Inflated; cm)Difference in Balloon Circumference (cm)
1 – (Cold)
2 – (Room Temp.)
3 – (Hot)

Take a picture of your results. Include a note with your name and date on an index card in the picture. Insert picture here (3 points):

Post-Lab Questions

1. What reaction is being catalyzed in this experiment? (2 points)

2. A) What is the enzyme in this experiment? b) What is the substrate? (2 points each part = 4 points)

a
b

3. A) What is the independent variable in this experiment? b) What is the dependent variable? (2 point each part = 4 points)

a
b

4. How does the temperature affect enzyme function? Use evidence from your data to support your answer. (2 points)

5. A) Draw a graph of YOUR DATA for balloon diameter vs. temperature. Scan or photograph your graph and insert the image in the space below. Graph must have title (0.5 points), x-axis label and units (1 point), y-axis label and units (1 point), data points (1.5 points), line (1 point) (part a = total of 5 points) B) What is the correlation? ( part b = 2 points)

a
b

6. Is there a negative control in this experiment? If yes, identify the control. If no, suggest how you could revise the experiment to include a negative control. (2 points)

7. A) In general, how would an increase in substrate alter enzyme activity? . (part a = 2 points)

B) Draw a graph to illustrate this general relationship. This graph can be general but should still have a title (1 point) and labels for the axes (2 points), and a line (1 point) Scan or photograph your graph and insert the image in the space below. (part b = 5 points)

a
b

8. A) Design an experiment to determine the optimal temperature for enzyme function, complete with controls. B) Where would you find the enzymes for this experiment? C) What substrate would you use? (part a = 7 points, part b = 3 points, part c = 3 points)

a
b
c

TYPE YOUR FULL NAME:

Biology labs

Pre-Lab Questions

1. What are chromosomes made of?

2. Research the differences that exist between mitosis and binary fission. Identify at least one difference, and explain why it is significant.

3. Cancer is a disease related to uncontrolled cell division. Investigate two known causes for these rapidly dividing cells and use this knowledge to invent a drug that would inhibit the growth of cancer cells.

Experiment 1: Observation of Mitosis in a Plant Cell

In this experiment, we will look at the different stage of mitosis in an onion cell. Remember that mitosis only occupies one to two hours while interphase can take anywhere from 18 – 24 hours. Using this information and the data from your experiment, you can estimate the percentage of cells in each stage of the cell cycle.

image9.jpg
MaterialsOnion (allium) Root Tip Digital Slide Images

Procedure:

Part 1: Calculating Time Spent in Each Cell Cycle Phase

1. The length of the cell cycle in the onion root tip is about 24 hours. Predict how many hours of the 24 hour cell cycle you think each step takes. Record your predictions, along with supporting evidence, in Table 1.

2. Examine the onion root tip slide images on the following pages. There are four images, each displaying a different field of view. Pick one of the images, and count the number of cells in each stage. Then count the total number of cells in the image. Record the image you selected and your counts in Table 2.

3. Calculate the time spent by a cell in each stage based on the 24 hour cycle:

Hours of Stage =24 x Number of Cells in Stage 
 Total Number of Cells Counted

Part 2: Identifying Stages of the Cell Cycle

1. Observe the images of the root cap tip.

2. Locate a good example of a cell in each of the following stages: interphase, prophase, metaphase, anaphase, and telophase.

3. Draw the dividing cell in the appropriate area for each stage of the cell cycle, exactly as it appears. Include your drawings in Table 3.

Onion Root Tip: 100X
Onion Root Tip: 100X
Onion Root Tip: 100X
Onion Root Tip: 100X
Table 1: Mitosis Predictions
Predictions: 
Supporting Evidence: 
Table 2: Mitosis Data
Number of Cells in Each StageTotal Number of CellsCalculated % of Time Spent in Each Stage
Interphase: Interphase:
Prophase:Prophase:
Metaphase:Metaphase:
Anaphase:Anaphase:
Telophase:Telophase:
Cytokinesis:Cytokinesis:
Table 3: Stage Drawings
Cell Stage:Drawing:
Interphase: 
Prophase: 
Metaphase: 
Anaphase: 
Telophase: 
Cytokinesis: 

Post-Lab Questions

1. Label the arrows in the slide image below with the appropriate stage of the cell cycle.

image5.png

2. In what stage were most of the onion root tip cells? Based on what you know about cell cycle division, what does this imply about the life span of a cell?

3. Were there any stages of the cell cycle that you did not observe? How can you explain this using evidence from the cell cycle?

4. As a cell grows, what happens to its surface area to volume ratio? (Hint: Think of a balloon being blown up). How does this ratio change with respect to cell division?

5. What is the function of mitosis in a cell that is about to divide?

6. What would happen if mitosis were uncontrolled?

7. How accurate were your time predication for each stage of the cell cycle?

8. Discuss one observation that you found interesting while looking at the onion root tip cells.

Experiment 2: Tracking Chromosomal DNA Movement through Mitosis

image10.jpg

Although mitosis and meiosis share similarities, they are different processes and create very different results. In this experiment, you will follow the movement of the chromosomes through mitosis to create somatic daughter cells.

Materials2 Sets of Different Colored Pop-it® Beads (32 of each – these may be any color) (8) 5-Holed Pop-it® Beads (used as centromeres)

Procedure

Genetic content is replicated during interphase. DNA exists as loose molecular strands called chromatin; it has not condensed to form chromosomes yet.

Sister chromatids begin coiling into chromosomes during prophase. Begin your experiment here:

1. Build a pair of replicated, homologous chromosomes. 10 beads should be used to create each individual sister chromatid (20 beads per chromosome pair). Two five-holed beads represent each centromere. To do this…

Figure 5: Bead set-up. The blue beads represent one pair of sister chromatids and the black beads represent a second pair of sister chromatids. The black and blue pair are homologous.

a. Start with 20 beads of one color to create your first sister chromatid pair. Five beads must be snapped together for each of the four different strands. Two strands create the first chromatid, and two strands create the second chromatid.

b. Place one five-holed bead flat on a work surface with the node positioned up. Then, snap two of the four strands into the bead to create an “I” shaped sister chromatid. Repeat this step with the other two strands and another five-holed bead.

c. Once both sister chromatids are constructed, connect them by their five-holed beads creating an “X” shape.

d. Repeat this process using 20 new beads (of a different color) to create the second sister chromatid pair. See Figure 5 for reference.

2. Assemble a second pair of replicated sister chromatids; this time using 12 beads, instead of 20, per pair (six beads per each complete sister chromatid strand).

Figure 6: Second set of replicated chromosomes.

3. Repeat this process using 12 new beads (of a different color) to create the second set of sister chromatids. See Figure 6 for reference.

4. Configure the chromosomes as they would appear in each of the stages of the cell cycle (prophase, metaphase, anaphase, telophase, and cytokinesis). Diagram the images for each stage in the section titled “Cell Cycle Division: Mitosis Beads Diagram”. Be sure to indicate the number of chromosomes present in each cell for each phase.

Cell Cycle Division: Mitosis Beads Diagram:

Prophase

Metaphase

Anaphase

Telophase

Cytokinesis

Post-Lab Questions

1. How many chromosomes did each of your daughter cells contain?

2. Why is it important for each daughter cell to contain information identical to the parent cell?

3. How often do human skin cells divide? Why might that be? Compare this rate to how frequently human neurons divide. What do you notice?

4. Hypothesize what would happen if the sister chromatids did not split equally during anaphase of mitosis.

Experiment 3: The Importance of Cell Cycle Control

Some environmental factors can cause genetic mutations which result in a lack of proper cell cycle control (mitosis). When this happens, the possibility for uncontrolled cell growth occurs. In some instances, uncontrolled growth can lead to tumors, which are often associated with cancer, or other biological diseases.

image11.jpg

In this experiment, you will review some of the karyotypic differences which can be observed when comparing normal, controlled cell growth and abnormal, uncontrolled cell growth. A karyotype is an image of the complete set of diploid chromosomes in a single cell.

Materials*Computer Access *Internet Access*You Must Provide

Procedure

1. Begin by constructing a hypothesis to explain what differences you might observe when comparing the karyotypes of human cells which experience normal cell cycle control versus cancerous cells (which experience abnormal, or a lack of, cell cycle control). Record your hypothesis in Post-Lab Question 1. Note: Be sure to include what you expect to observe, and why you think you will observe these features. Think about what you know about cancerous cell growth to help construct this information

2. Go online to find some images of abnormal karyotypes, and normal karyotypes. The best results will come from search terms such as “abnormal karyotype”, “HeLa cells”, “normal karyotype”, “abnormal chromosomes”, etc. Be sure to use dependable resources which have been peer-reviewed

3. Identify at least five abnormalities in the abnormal images. Then, list and draw each image in the Data section at the end of this experiment. Do these abnormalities agree with your original hypothesis? Hint: It may be helpful to count the number of chromosomes, count the number of pairs, compare the sizes of homologous chromosomes, look for any missing or additional genetic markers/flags, etc.

Data

1.

2.

3.

4.

5.

Post-Lab Questions

1. Record your hypothesis from Step 1 in the Procedure section here.

2. What do your results indicate about cell cycle control?

3. Suppose a person developed a mutation in a somatic cell which diminishes the performance of the body’s natural cell cycle control proteins. This mutation resulted in cancer, but was effectively treated with a cocktail of cancer-fighting techniques. Is it possible for this person’s future children to inherit this cancer-causing mutation? Be specific when you explain why or why not.

Pre-Lab Questions

1. Arrange the following molecules from least to most specific with respect to the original nucleotide sequence: RNA, DNA, Amino Acid, Protein

2. Identify two structural differences between DNA and RNA.

3. Suppose you are performing an experiment in which you must use heat to denature a double helix and create two single stranded pieces. Based on what you know about nucleotide bonding, do you think the nucleotides will all denature at the same time? Use scientific reasoning to explain why.

Experiment 1: Coding

In this experiment, you will model the effects of mutations on the genetic code. Some mutations cause no structural or functional change to proteins while others can have devastating affects on an organism.

image12.png
MaterialsRed BeadsBlue BeadsYellow BeadsGreen Beads

Procedure:

1. Using the red, blue, yellow and green beads, devise and lay out a three color code for each of the following letters (codon). For example Z = green : red : green.

In the spaces below the letter, record your “code”.

C:E:H:I:K:L:
bbbgggrrryyybgrGrb
M:O:S:T:U:
yrgybybybRgrGyg
Create codons for:Start:Stop:Space:
 bbrggryyr

2. Using this code, align the beads corresponding to the appropriate letter to write the following sentence (don’t forget start, space and stop): The mouse likes most cheese

a. How many beads did you use? 87

There are multiple ways your cells can read a sequence of DNA and build slightly different proteins from the same strand. We will not go through the process here, but as an illustration of this “alternate splicing”, remove codons (beads) 52 – 66 from your sentence above.

b. What does the sentence say now? (re-write the entire sentence) The mouse likes cheese

Mutations are simply changes in the sequence of nucleotides. There are three ways this occurs:

1. Change a nucleotide(s)

2. Remove a nucleotide(s)

3. Add a nucleotide(s)

3. Using the sentence from exercise 1B:

a. Change the 24th bead to a different color. What does the sentence say now (re-read the entire sentence)? Does the sentence still make sense?

The moose likes cheese

b. Replace the 24th bead and remove the 20th bead (remember what was there). What does the sentence say (re-read the entire sentence)? Does the sentence still make sense? If it doesn’t make sense as a sentence, are there any words that do? If so, what words still make sense?

The muse likes cheese

c. Replace the 20th bead and add one between bead numbers 50 and 51. What does the sentence say now? Does the sentence still make sense?

d. In 3.a (above) you mutated one letter. What role do you think the redundancy of the genetic code plays in this type of change?

e. Based on your observations, why do you suppose the mutations we made in 3.b and 3.c are called frame shift mutations?

f. Which mutations do you suspect have the greatest consequence? Why?

Experiment 2: Transcription and Translation

DNA codes for all of the proteins manufactured by any organism (including you!). It is valuable, highly informative and securely protected in the nucleus of every cell. Consider the following analogy:

An architect spends months or years designing a building. Her original drawings are valuable and informative. She will not provide the original copy to everyone involved in constructing the building. Instead, she gives the electrician a copy with the information she needs to build the electrical system. She will do the same for the plumbers, the framers, the roofers and everyone else who needs to play a role to build the structure. These are subsets of the information contained in the original copy. Your cell does the same thing. The “original drawings” are contained in your DNA which is securely stored in the nucleus.

Nuclear DNA is “opened up” by an enzyme called helicase, and a subset of information is transcribed into RNA. RNA is a single strand version of DNA, where the nucleotide uracil, replaces thymine. The copies are sent from the nucleus to the cytoplasm in the form of messenger RNA (mRNA ). Once in the cytoplasm, transfer RNA (tRNA) links to the codons and aligns the proper amino acids, based on the mRNA sequence. Protein builders called ribosomes float around in the cytoplasm, latch onto the strand of mRNA and sequentially link the amino acids together that the tRNA has lined up for them. This construction of proteins from the mRNA is known as translation.

image13.jpg
MaterialsBlue beads Green beads Red beads Yellow beads Pop-it® beads (8 different colors) *Pen or pencil*You Must Provide In this experiment:· Regular beads are used as nucleotides.· Pop-it® beads are used as amino acids.

Procedure

1. Use a pen or pencil to write a five word sentence using no more than eight different letters in the space below.

2. Now, use the red, blue, green, and yellow beads to form “codons” (three beads) for each letter in your sentence. Then, create codons to represent the “start, “space” and stop” regions within your sentence. Write the sentence using the beads in the space below:

3. How many beads did you use?

4. Assign one Pop-It® bead to represent each codon. You do not need to assign a Pop-It® bead for the start, stop and space regions. These will be your amino acids.

5. Connect the Pop-It® beads to build the chain of amino acids that code for your sentence (leave out the start, stop, and space regions).

6. How many different amino acids did you use?

7. How many total amino acids did you use?

Experiment 3: DNA Extraction

image14.jpg

Much can be learned from studying an organism’s DNA. The first step to doing this is extracting DNA from cells. In this experiment, you will isolate DNA from the cells of fruit.

Materials(1) 10 mL Graduated Cylinder (2) 100 mL Beakers 15 cm Cheesecloth 1 Resealable Bag 1 Rubber Band (Large. Contains latex; please wear gloves when handling if you have a latex allergy). Standing Test Tube Wooden Stir Stick *Fresh, Soft Fruit (e.g., Grapes, Strawberries, Banana, etc.)*Scissors **DNA Extraction Solution ***Ice Cold Ethanol *You Must Provide **Contains sodium chloride, detergent and water ***For ice cold ethanol, store in the freezer 60 minutes before use.

REMINDER: You are REQUIRED to video yourself performing steps 3 through 9 of the procedure below. You MUST submit the video with the lab to receive credit for this experiment.

Procedure:

1. If you have not done so, prepare the ethanol by placing it in a freezer for approximately 60 minutes.

2. Put pieces of a soft fruit into a plastic zipper bag and mash with your fist. The amount of food should be equal to the size of approximately five grapes.

3. Use the 10 mL graduated cylinder to measure 10 mL of the DNA Extraction Solution. Transfer the solution from the cylinder to the bag with the fruit it in. Seal the bag completely.

4. Mix well by kneading the bag for two minutes.

5. Create a filter by placing the center of the cheesecloth over the mouth of the standing test tube, pushing it into the tube about two inches, and securing the cheesecloth with a rubber band around the top of the test tube.

6. Cut a hole in the corner of the bag and filter your extraction by pouring it into the cheesecloth. You will need to keep the filtered solution which passes through the cheese cloth into the standing test tube.

7. Rinse the 10 mL graduated cylinder, and measure five mL of ice-cold ethanol. Then, while holding the standing test tube at a 45° angle, slowly transfer the ethanol into the standing test tube with the filtered solution.

Figure 6: DNA extraction. The color has been enhanced by dying the fruit with a substance that glows under black light.

8. DNA will precipitate (come out of solution) after the ethanol has been added to the solution. Let the test tube sit undisturbed for 2 – 5 minutes. You should begin to see air bubbles form at the boundary line between the ethanol and the filtered fruit solution. Bubbles will form near the top, and you will eventually see the DNA float to the top of the ethanol.

9. Gently insert the stir stick into the test tube. Slowly raise and lower the tip several times to spool and collect the DNA. If there is an insufficient amount of DNA available, it may not float to the top of the solution in a form that can be easily spooled or removed from the tube. However, the DNA will still be visible as white/clear clusters by gently stirring the solution and pushing the clusters around the top.

Post-Lab Questions

1. What is the texture and consistency of the DNA?

2. Why did we use a salt in the extraction solution?

3. Is the DNA soluble in the aqueous solution or alcohol?

4. What else might be in the ethanol/aqueous interface? How could you eliminate this?

5. Which DNA bases pair with each other? How many hydrogen bonds are shared by each pair?

6. How is information to make proteins passed on through generations?

Pre-Lab Questions

1. In a species of mice, brown fur color is dominant to white fur color. When a brown mouse is crossed with a white mouse all of their offspring have brown fur. Why did none of the offspring have white fur?

2. Can a person’s genotype be determine by their phenotype? Why or why not?

3. Are incomplete dominant and co-dominant patterns of inheritance found in human traits? If yes, give examples of each.

4. Consider the following genotype: Yy Ss Hh. We have now added the gene for height: Tall (H) or Short (h).

a. How many different gamete combinations can be produced?

b. Many traits (phenotypes), like eye color, are controlled by multiple genes. If eye color were controlled by the number of genes indicated below, how many possible genotype combinations would there be in the following scenarios?

5 Eye Color Genes:

10 Eye Color Genes:

20 Eye Color Genes:

Experiment 1: Punnett Square Crosses

In this experiment you will use monohybrid and dihybrid crosses to predict patterns of inheritance.

image15.jpg
MaterialsBlue Beads Green Beads Red BeadsYellow Beads (2) 100 mL Beakers Permanent Marker

Procedure:

Part 1: Punnett Squares

1. Set up and complete Punnett squares for each of the following crosses: (remember Y = yellow, and y = blue)

Y Y and Y yY Y and y y

2. What are the resulting phenotypes?

3. Are there any blue kernels? How can you tell?

4. Set up and complete a Punnett squares for a cross of two of the F1 from Step 1 (above).

5. What are the genotypes of the F2 generation?

6. What are their phenotypes?

7. Are there more or less blue kernels than in the F1 generation?

8. Identify the four possible gametes produced by the following individuals:

a)YY Ss: __________________ ______
b)Yy Ss:________________________
c)Create a Punnett square using these gametes as P and determine the genotypes of the F1:

What are the phenotypes? What is the ratio of those phenotypes?

Part 2 and 3 Setup

1. Use the permanent marker to label the two 100 mL beakers as “1” and “2”.

2. Pour 50 of the blue beads and 50 of the yellow beads into Beaker 1. Sift or stir the beads around to create a homogenous mixture.

3. Pour 50 of the red beads and 50 of the green beads into Beaker 2. Sift or stir the beads around to create a homogenous mixture.

Assumptions for the remainder of the experiment:

· Beaker 1 contains beads that are either yellow or blue.

· Beaker 2 contains beads that are either green or red.

· Both beakers contain approximately the same number of each colored bead.

· These colors correspond to the following traits (remember that Y/y is for kernel color and S/s is for smooth/wrinkled):

1. Yellow (Y) vs. Blue (y)

2. Green (G) vs. Red (g).

Part 2: Monohybrid Cross

1. Randomly (without looking) take two beads out of Beaker 1. This is the genotype of Individual #1. Record the genotype in Table 1. Do not put these beads back into the beaker.

Table 1: Parent Genotypes: Monohybrid Crosses
GenerationGenotype of Individual 1Genotype of Individual 2
P  
P1  
P2  
P3  
P4  

2. Repeat Step 1 for Individual #2. These two genotypes represent the parents (generation P) for the next generation.

3. Set up a Punnett square and determine the genotypes and phenotypes for this cross. Record your data in Table 2

4. Repeat Step 3 four more times (for a total of five subsequent generations). Return the beads to their respective beakers when finished.

Table 2: Generation Data Produced by Monohybrid Crosses
ParentsPossible Offspring GenotypesPossible Offspring PhenotypesGenotype RatioPhenotype Ratio
P    
P1    
P2    
P3    
P4    

Post-Lab Questions

Part 2: Monohybrid Cross

1. How much genotypic variation do you find in the randomly picked parents of your crosses?

2. How much in the offspring?

3. How much phenotypic variation?

4. Is the ratio of observed phenotypes the same as the ratio of predicted phenotypes? Why or why not?

5. Pool all of the offspring from your five replicates. How much phenotypic variation do you find?

6. What is the difference between genes and alleles?

7. How might protein synthesis execute differently if a mutation occurs?

8. Organisms heterozygous for a recessive trait are often called carriers of that trait. What does that mean?

9. In peas, green pods (G) are dominant over yellow pods. If a homozygous dominant plant is crossed with a homozygous recessive plant, what will be the phenotype of the F1 generation? If two plants from the F1 generation are crossed, what will the phenotype of their offspring be?

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Microscopy for Microbiology – Use and Function Hands-On Labs, Inc. Version 42-0249-00-02

Lab Report Assistant

This document is not meant to be a substitute for a formal laboratory report. The Lab Report Assistant is simply a summary of the experiment’s questions, diagrams if needed, and data tables that should be addressed in a formal lab report. The intent is to facilitate students’ writing of lab reports by providing this information in an editable file which can be sent to an instructor.

Exercise 1: Getting to Know your Compound Microscope

Data Table 1. Microscope Components.

LetterComponent NameComponent Function
A
B
C
D
E
F
G
H
I
J
K
L
M

Data Table 2. Total Magnification.

LensOcular MagnificationObjective MagnificationTotal Magnification
Scanning
Low Power
High Power
Oil Immersion

Data Table 3. Field of View.

LensTotal MagnificationField of View (mm)Field of View (µM)
Scanning
Low Power
High Power
Oil Immersion

Data Table 4. Letter e Viewing Results.

LensPhotographObservations
Scanning
Low
High
Oil Immersion

Questions

A. Describe the details in the slides “Letter e” that become visible as the power changed from scanning power, to low power, to high power.

B. Why is it important to calculate the diameter of the field when first using the microscope?

Exercise 2: Viewing Prepared Microbe Slides

Data Table 5. Prepared Slide Viewing Results.

SlidePhotographTotal Magnification
Amoeba
Penicillium
Yeast
Spirillium
Bacillus
Coccus

Questions

A. Using the field of view calculated in Exercise 1 for the high power lens, approximately how far across are each of the cells in the Bacteria Coccus Form slide in Data Table 5? Show your calculations.

B. Detail techniques you found helpful for focusing on the various slides in this exercise.

Exercise 3: Preparing Wet-Mount Slides

Data Table 6. Wet-Mount Viewing Results.

SlidePhotographTotal Magnification
Cheek Cell Smear
Dental Tatar Smear

Questions

A. Describe the similarities and differences between the cheek cell wet mount and dental plaque wet mount.

B. How did the process of preparing wet-mount slides become easier as you prepared the second wet-mount slide of this exercise?

Microscopy for Microbiology – Use and Function Hands-On Labs, Inc. Version 42-0249-00-02

Review the safety materials and wear goggles when working with chemicals. Read the entire exercise before you begin. Take time to organize the materials you will need and set aside a safe work space in which to complete the exercise.

Experiment Summary:

You will identify the components of an optical microscope. You will describe field of view and depth of field. You will view a series of preserved specimens including protozoans, fungi, and bacteria. You will prepare wet mounts of cheek cells and dental tartar.

EXPERIMENT

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Learning Objectives Upon completion of this laboratory, you will be able to:

● Outline the components of an optical microscope.

● Describe field of view and depth of field.

● Calculate the total magnification and field of view for the lenses of an optical microscope.

● Examine prepared slides under scanning, low, high, and oil immersion lenses.

● Prepare wet mounts of cheek cells and dental plaque and examine them under different lenses.

Time Allocation: 3.5 hours

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Experiment Microscopy for Microbiology – Use and Function

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Experiment Microscopy for Microbiology – Use and Function

Materials Student Supplied Materials

Quantity Item Description 1 Camera, digital or smartphone 1 Distilled water 1 Roll of paper towels

HOL Supplied Materials

Quantity Item Description 2 Blank slides 1 Pair of gloves 1 Lens paper (50 sheets) 1 Long thin stem pipet 1 Metric ruler 1 Safety goggles 1 Slide Box:

1 – Slide – Amoeba, whole mount 1 – Slide – Bacteria bacillus form 1 – Slide – Bacteria coccus form 1 – Slide – Bacteria spirillum 1 – Slide – Letter e focusing slide 1 – Slide – Penicillium with Conidia 1 – Slide – Yeast, whole mount

1 Slide cover glass cube 1 Sterile swabs, 2 per pack 1 Student microscope with 100x oil immersion lens*

1 – Immersion Oil

*Microscopes and oil immersion lens are purchased separately from the LabPaq kit.

Note: To fully and accurately complete all lab exercises, you will need access to:

1. A computer to upload digital camera images.

2. Basic photo editing software, such as Microsoft Word® or PowerPoint®, to add labels, leader lines, or text to digital photos.

3. Subject-specific textbook or appropriate reference resources from lecture content or other suggested resources.

Note: The packaging and/or materials in this LabPaq kit may differ slightly from that which is listed above. For an exact listing of materials, refer to the Contents List included in your LabPaq kit.

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Experiment Microscopy for Microbiology – Use and Function

Background Optical Microscopes

A microscope is an optical instrument that uses a lens or a series of lenses to magnify objects that are either too small to be seen by the naked eye, or to view distinct details of an object that are not visible to the naked eye. There are three main categories of microscopes: optical, electron, and scanning probe.

Optical microscopes, also referred to as light microscopes, use reflected visible light and a series of two or more convex lenses to magnify and focus an object. The most common type of light microscope is the compound microscope, which utilizes a lens of short focal length and a second lens of a longer focal length. The short lens forms and focuses the image, and the longer lens magnifies and further focuses the image. Compound microscopes are able to resolve objects to a resolution of approximately 200 nm (0.2 µm). Resolving power is the ability to discern two objects as separate, and is limited by the wavelength of light. As compound microscopes utilize reflected visible light, the resolution of the microscope is limited by the wavelength of the visible light.

The components of a compound microscope work together to create a magnified image. See Figure 1. The description of each of the parts is discussed on the following page.

Figure 1. Main components of a compound microscope. © Picsfive

The ocular lens is located at the top of the microscope. This short lens is termed “ocular” as it the lens that one looks through in order to view the image. An ocular lens is typically 10x or 15x power and is often referred to as the eye piece. A microscope with one ocular lens is called a monocular microscope, a microscope with two ocular lenses is called a binocular microscope (as shown in Figure 1), and a microscope with two ocular lenses and a location for a camera is called a trinocular microscope.

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Experiment Microscopy for Microbiology – Use and Function

The objective lenses of a microscope are found closest to the stage and are held by the turret, or revolving nose piece. The turret allows the lenses to be easily rotated to select the lens that offers the necessary power of magnification. There are typically three to four objective lenses on a microscope, ranging in power from 4x to 100x. The lowest power objective lens (4x) is the scanning lens, the medium strength objective lens (10x) is the low power lens, and the highest strength objective lens (40x) is the high power lens. If a fourth objective lens is present it is typically the 100x oil immersion lens. Oil immersion lenses are typically spring-loaded and retractable, so that the end of the lens will retract if it comes into contact with the object, protecting both the slide and the lens from damage. Additionally, an oil immersion lens is generally sealed, keeping the oil from seeping into the lens. The total magnification factor of a microscope is calculated by multiplying the magnification of the ocular lens with the magnification of the objective lens. For example, if the ocular lens has a magnification of 15x and the objective lens has a total magnification of 40x, the total magnification factor is 600x: 15 x 40 = 600.

Related to the total magnification factor are the field of view and depth of field. The higher the total magnification factor, the smaller the field of view. For example, imagine looking at a book at a distance of 3 feet. At this distance there is a large field of view, or the visible area that can be observed. In this case, the entire book is visible, along with its location relative to other objects. As the distance between your eye and the book is decreased, so is the field of view. If you are holding a book only an inch from your eye, not only is there a loss of dimensionality (from 3D to 2D), only a few words on the cover will be visible instead of the entire book. This is analogous to viewing an object with a microscope: by increasing the magnification, the field of view (or amount of the object seen) is smaller, and more detail is visible.

Depth of field refers to the distance range that is in focus at a given time. This concept is also relevant in photography, where a photographer can adjust the depth of focus to have either a shallow focus that will emphasize a subject, or a greater focus, that will focus to include much of the foreground and background. Like field of view, the depth of view is dependent on the total magnification factor. Compound microscopes have an inherently shallow depth of field, on the order of only a few micrometers. See Figure 2.

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Experiment Microscopy for Microbiology – Use and Function

Figure 2. Depth of field. The left image shows a shallow depth of field. Notice that everything but the hand is out of focus. © Moisa The right image shows a greater depth of field. Notice that

not only is the hand in focus, but the surrounding image is as well. Note the focus of the buttons on the suit. © Provasilich

The arm of a microscope supports the lenses of the microscope and connects them to the base of the microscope. The base is the bottom of the microscope, which provides support to the instrument. When moving a microscope from one location to another, place one hand around the arm, and the other under the base.

The object (mounted on a slide) to be viewed with the microscope is placed on the stage. The stage is the flat platform with stage clips to hold the slide in place. A mechanical stage is a movable platform that allows the user to move the slide left and right, or forward and backward, by turning the stage adjustment knobs. This feature is useful for moving a slide in small increments, and also for recording and relocating the slide to a specific point of interest.

The illuminator is the light source (plug-in light, battery-powered light, or mirror to reflect light), which illuminates the object. The condenser lens sits just below the stage, and focuses the light from the illuminator onto the slide. The diaphragm sits below the stage and the condenser lens. It is composed of overlapping pieces of metal or plastic that move to vary the amount of light projected toward the condenser lens. Microscopes with a diaphragm have a small lever that is used to change the size of the opening, which adjusts the intensity of light. While there is not a set amount of light required to view slides, the intensity of light is a personal preference of the person using the microscope. See Figure 3.

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Experiment Microscopy for Microbiology – Use and Function

Figure 3. Diaphragm. The photo on the left shows the diaphragm letting little light through. The right-hand photo shows the diaphragm letting much more light through. © Luzanin

The focus adjustment knobs adjust the distance between the slide and the object lens, by moving the stage up and down. The coarse adjustment knob (coarse focus knob) is used when larger amounts of focus are needed and moves the stage a greater distance than the fine adjustment knob (fine focus knob). The fine focus knob is used for focusing at higher powers of magnification and moves the stage in very small increments.

If you ever go to a sporting event and sit high in the bleachers, you might bring a pair of binoculars

to help you see the event on the field by magnifying the field of view. However, binoculars are not microscopes; they are actually a variant of a telescope. A telescope is a device that utilizes a system of mirrors and lenses to make distant objects appear larger and brighter. This is

in contrast to a microscope, which magnifies objects close to the eye.

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Experiment Microscopy for Microbiology – Use and Function

Exercise 1: Getting to Know your Compound Microscope In this exercise you will identify and describe the components of a compound microscope. You will calculate the total magnification and diameter of field. You will then practice focusing your microscope on a prepared slide.

1. Gather the microscope. Assemble the microscope (if necessary).

2. Use the information in the Background section, a text book (as necessary), and the image of your student microscope in Figure 1, to identify the name of each of the lettered components of Figure 4. Record the name of each microscope component in Data Table 1 of your Laboratory Report Assistant.

Figure 4. Student compound microscope, with letters. Use for Data Table 1.

3. Describe the function of each identified microscope component in Data Table 1.

4. Look at the ocular lens and each of the objective lenses of your microscope. Determine which of the objective lenses are the scanning power, the low power, and the high power. Make sure to include the oil immersion lens in your observations.

5. Record the power of magnification of each of the lenses in Data Table 2 of your Laboratory Report Assistant.

6. Calculate and record the total magnification for each of the different lens combinations in Data Table 2.

Note: If assistance is necessary, review the information provided in the Background section.

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Experiment Microscopy for Microbiology – Use and Function

Calculating the Field of View

7. Place the metric ruler onto the stage of the microscope so that the metric side of the ruler (mm markings) is in the center of the light path.

Note: The ruler must rest on top of the stage, and thus must be manually held in place. Do not try to affix the ruler under the stage clips.

Note: The field of view is the circle visible through the lenses. The diameter of field is the length of the field from one edge of the circle to the other, passing through the middle of the circle. See Figure 5.

Figure 5. Field of view. Align the middle of the markings to the center of the circle.

8. Focus the ruler with the scanning lens.

Note: It may require minor adjustments to clearly focus the ruler. Make sure to adjust both the stage adjustment knobs and the focus knobs as necessary to obtain a focused view.

9. Record the approximate field of view for the scanning power in millimeters in Data Table 3 of your Laboratory Report Assistant.

10. Convert the field of view from millimeters to micrometers and record in Data Table 3.

Note: 1 millimeter is equal to 1000 micrometers.

11. Repeat steps 8-10 for the low power lens.

12. Use the following formula to calculate the field of view for the high power lens and record in Data Table 3:

13. Convert the field of view from millimeters to micrometers and record in Data Table 3.

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Experiment Microscopy for Microbiology – Use and Function

Focusing and Using the Microscope

14. Identify the “Letter e” slide in your slide box.

Note: Use the lens paper, as necessary, to wipe the slides prior to placing them on the microscope.

15. Place the “Letter e” slide on the stage, between the stage clips, and turn on the light. See Figure 6.

Figure 6. Student microscope with slide and illuminator on.

16. Switch the objective lens to the scanning power and use the focus adjustment knobs, as necessary, to focus the image on the slide.

17. Use a digital camera, camera phone, or microscope camera to take a photograph of the slide. Refer to the appendix entitled “Taking Microscope Photos” for guidance with taking microscope photos with a digital camera. See Figure 7.

Figure 7. Photograph of “Letter e” slide as taken with a digital camera through microscope eyepiece.

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Experiment Microscopy for Microbiology – Use and Function

18. Take the image and resize, then insert the photograph of the “Letter e” slide on scanning power in Data Table 4 of your Laboratory Report Assistant. Refer to the appendix entitled “Resizing an Image” for guidance with resizing an image.

19. Using your observations, describe the details that are visible when viewing the slide at scanning power in Data Table 4.

20. Switch the objective lens to low power, and use the focus adjustment knobs, as necessary, to focus the image on the “Letter e” slide.

21. Repeat steps 17-19.

22. Switch the objective lens to high power and use the focus adjustment knobs, as necessary, to focus the image on the “Letter e” slide.

23. Repeat steps 17-19.

24. Install the oil immersion 100x objective lens in place of the scanning lens.

25. Apply a drop of immersion oil on the specimen slide and turn the revolving nosepiece to bring the 100x lens into position.

26. With the lens tip touching the oil, focus with the fine adjustment knob.

27. Repeat steps 17-19.

28. After using the oil immersion lens replace it with the scanning power lens and wipe the immersion lens tip with lens paper. Clean the slide with soap and water and return it to your kit.

Questions A. Describe the details in the “Letter e” slide that become visible as the power changed from

scanning power, to low power, to high power.

B. Why is it important to calculate the diameter of the field when first using the microscope?

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Experiment Microscopy for Microbiology – Use and Function

Exercise 2: Viewing Prepared Microbe Slides In this exercise you will view a series of prepared slides to gain proficiency with observing microbes.

1. Gather the microscope, oil immersion lens, immersion oil, lens paper, and the following prepared slides: “Amoeba, Whole Mount”, “Penicillium with Conidia”, “Yeast, Whole Mount”, “Bacteria Spirillum”, “Bacteria Bacillus Form”, and “Bacteria Coccus Form”.

2. Place the “Amoeba, Whole Mount” slide on the microscope state and focus under scanning power.

3. Refer to Figure 8 when locating the microbe on the slide.

Figure 8. Amoeba, Whole Mount at 100x magnification.

4. Switch the objective lens to the low power and focus on the microbe.

5. Switch the objective lens to high power and focus on the microbe.

6. Replace the scanning power objective with the oil immersion lens.

7. Add a drop of immersion oil to the slide and move the 100x lens into position. Adjust the fine adjustment knob as needed to bring the image into focus.

8. Determine which objective lens is best for viewing the specimen and take a photo of the image.

9. Resize and insert the photograph of the specimen in Data Table 5 of your Laboratory Report Assistant.

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Experiment Microscopy for Microbiology – Use and Function

10. Record the objective and total magnification used for the photo in Data Table 5.

11. Replace the oil immersion lens with the scanning lens and wipe the removed lens tip with lens paper.

12. Replace the “Amoeba, Whole Mount” slide with the “Penicillium with Condidia” on the microscope stage and focus under scanning power.

13. Refer to Figure 9 when locating the specimen on the slide.

Figure 9. Penicillium with Conidia under 400x magnification.

14. Repeat steps 4-11 for this slide.

15. Replace the “Penicillium with Conidia” slide with the “Yeast, Whole Mount” slide on the microscope stage and focus on scanning power.

16. Refer to the image in Figure 10 when locating the specimen on the slide.

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Experiment Microscopy for Microbiology – Use and Function

Figure 10. Yeast, Whole Mount under 400x magnification.

17. Repeat steps 4-11 for this slide.

18. Replace the “Yeast, Whole Mount” slide with the “Bacteria Spirillum” slide on the microscope stage and focus on scanning power.

19. Refer to image in Figure 11 when locating the specimen on the slide.

Figure 11. Bacteria Spirillum under 400x magnification.

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Experiment Microscopy for Microbiology – Use and Function

20. Repeat steps 4-11 for this slide.

21. Replace the “Bacteria Spirillum” with “Bacteria Bacillus Form” on the microscope stage and focus on scanning power.

22. Refer to Figure 12 when locating the specimen on the slide.

Figure 12. Bacteria Bacillus Form under 400x magnification.

23. Repeat steps 4-11 for this slide.

24. Replace the “Bacteria Bacillus Form” slide with the “Bacteria Coccus Form” slide on the microscope stage and focus on scanning power.

25. Refer to Figure 13 when locating the specimen on the slide.

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Experiment Microscopy for Microbiology – Use and Function

Figure 13. Bacteria Coccus Form at 400x magnification.

26. Repeat steps 4-11 for this slide.

27. Remove the “Bacteria Coccus Form” slide from the microscope.

28. Clean and store all slides in the box provided.

Questions A. Using the field of view calculated in Exercise 1 for the high power lens, approximately how

far across are each of the cells in the Bacteria Coccus Form slide in Data Table 5? Show your calculations.

B. Detail techniques you found helpful for focusing on the various slides in this exercise.

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Experiment Microscopy for Microbiology – Use and Function

Exercise 3: Wet-Mount Slides In this exercise you will create wet-mount slides of cheek cells and tooth plaque and observe them under the microscope.

1. Gather your microscope, two blank slides, the cover slip cube, a long-stemmed pipet, 1 pack of sterile swabs, a pair of gloves, the safety goggles, paper towels and distilled water.

2. Place a sheet of paper towel onto your workspace to prevent the slides and cover slips from getting scratched.

3. Put on your gloves and safety goggles.

4. Gather a clean slide and cover slip and place them onto the paper towel.

5. Use one sterile swab from the package to gently scrape a few cells from the inside of your cheek.

6. Smear the swab containing the cheek cells onto the microscope slide. Carefully add one drop of distilled water with the long-stemmed pipet to the smear.

7. While holding the coverslip upright, carefully place one edge of the cover slip next to the water drop on the slide. As the drop of water comes into contact with the cover slip, the water will wick along the junction of the cover slip and the slide. See Figure 14.

Figure 14. Preparing a wet-mount slide.

8. Slowly lower the upper edge of the cover slip onto the water droplet.

9. If there is excess water, place a paper towel at the edge of the cover slip to draw out the excess water. This will further flatten the wet-mount slide.

10. Place the prepared slide on the microscope stage, between the stage clips, and turn on the light.

11. Focus on the cells under scanning power.

12. Refer to Figure 15 when locating the cells on the slide.

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Experiment Microscopy for Microbiology – Use and Function

Figure 15. Cheek cells at 400x magnification.

13. Switch the objective to low power and focus on the same cells.

14. Switch the objective to high power and focus on the cells.

Note: It may be necessary to reduce to the amount of light under the slide to clearly see the unstained cells.

15. Determine the best objective lens for viewing the slide and take a photo of the image at that magnification.

16. Resize and insert the photo into Data Table 6 of your Laboratory Report Assistant. Record the objective and total magnification in Data Table 6.

17. Gather the second sterile swab from the package and firmly rub it against your teeth near the gum line to collect dental plaque.

18. Repeat steps 6-16 with the dental plaque sample.

19. Wrap the wet-mounted slides, long-stemmed pipet, swabs, and safety gloves in paper towels and dispose of in the garbage.

20. Clean all equipment and return to your kit for future use.

21. When you are finished uploading photos and data into your Laboratory Report Assistant, save your file correctly and zip the file so you can send it to your instructor as a smaller file. Refer to the appendix entitled “Saving Correctly” and the appendix entitled “Zipping Files” for guidance with saving the Laboratory Report Assistant correctly and zipping the file.

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Experiment Microscopy for Microbiology – Use and Function

Questions A. Describe the similarities and differences between the cheek cell wet mount and dental plaque

wet mount.

B. How did the process of preparing wet-mount slides become easier as you prepared the second wet-mount slide of this exercise?