Microspcope And Cells Lab Report

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Microscopes and Cells

 

PRE-LAB ASSIGNMENT:

Students are expected to watch this video (which is also posted on Blackboard): https://www.youtube.com/watch?v= – b3Eejf4rDQ

AND read pages 1 to 4 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”.

 

Objectives:

After completing this laboratory assignment, students will be able to:

· Identify the parts of a compound microscope.

· Properly use a compound microscope for biological studies.

· Describe the features of specific cells.

· Determine characteristics shared by all cells studied.

 

Microscopes and Lenses:

Although cells vary in size, they’re generally quite small. For instance, the diameter of a typical human red blood cell is about eight micrometers (0.008 millimeters). To give you some context, the head of a pin is about one millimeter in diameter, so about 125 red blood cells could be lined up in a row across the head of a pin. With a few exceptions, individual cells cannot be seen with the naked eye, so scientists must instead use microscopes (micro– = “small”; –scope = “to look at”) to study them. A microscope is an instrument that magnifies objects otherwise too small to be seen, producing an image in which the object appears larger. Most photographs of cells are taken using a microscope, and these pictures can also be called micrographs. From the definition above, it might sound like a microscope is just a kind of magnifying glass. In fact, magnifying glasses do qualify as microscopes; since they have just one lens, they are called simple microscopes. The fancier instruments that we typically think of as microscopes are compound microscopes, meaning they have multiple lenses. Because of the way these lenses are arranged, they can bend light to produce a much more magnified image than that of a magnifying glass.

 

In a compound microscope with two lenses, the arrangement of the lenses has an interesting consequence: the orientation of the image you see is flipped in relation to the actual object you’re examining. For example, if you were looking at a piece of newsprint with the letter “e” on it, the image you saw through the microscope would be “ə.” More complex compound microscopes may not produce an inverted image because they include an additional lens that “re-inverts” the image back to its normal state.

 

What separates a basic microscope from a powerful machine used in a research lab? Two parameters are especially important in microscopy: magnification and resolution.

· Magnification is a measure of how much larger a microscope (or set of lenses within a microscope) causes an object to appear. For instance, the light microscopes typically used in high schools and colleges magnify up to about 400 times actual size. So, something that was 1 mm wide in real life would be 400 mm wide in the microscope image.

· The resolution of a microscope or a lens is the smallest distance by which two points can be separated and still be distinguished as separate objects. The smaller this value, the higher the resolving power of the microscope and the better the clarity and detail of the image. If two bacterial cells were very close together on a slide, they might look like a single, blurry dot on a microscope with low resolving power, but could be told apart as separate on a microscope with high resolving power.

 

Both magnification and resolution are important if you want a clear picture of something very tiny. For example, if a microscope has high magnification but low resolution, all you’ll get is a bigger version of a blurry image. Different types of microscopes differ in their magnification and resolution.

 

Light Microscopes:

Most student microscopes are classified as light microscopes. In a light microscope, visible light passes through the specimen (the biological sample you are looking at) and is bent through the lens system, allowing the user to see a magnified image. A benefit of light microscopy is that it can often be performed on living cells, so it’s possible to watch cells carrying out their normal behaviors (e.g., migrating or dividing) under the microscope.

 

Student lab microscopes tend to be brightfield microscopes, meaning that visible light is passed through the sample and used to form an image directly, without any modifications. Slightly more sophisticated forms of light microscopy use optical tricks to enhance contrast, making details of cells and tissues easier to see.

 

Another type of light microscopy is fluorescence microscopy, which is used to image samples that fluoresce (absorb one wavelength of light and emit another). Light of one wavelength is used to excite the fluorescent molecules, and the light of a different wavelength that they emit is collected and used to form a picture. In most cases, the part of a cell or tissue that we want to look at isn’t naturally fluorescent, and instead must be labeled with a fluorescent dye or tag before it goes on the microscope.

 

A confocal microscope is a specialized kind of fluorescence microscope that uses a laser to excite a thin layer of the sample and collects only the emitted light coming from the target layer, producing a sharp image without interference from fluorescent molecules in the surrounding layers.

 

Electron Microscopes:

Some cutting-edge types of light microscopy (beyond the techniques we discussed above) can produce very high-resolution images. However, if you want to see something very tiny at very high resolution, you may want to use a different, tried-and-true technique: electron microscopy.

 

Electron microscopes differ from light microscopes in that they produce an image of a specimen by using a beam of electrons rather than a beam of light. Electrons have a much shorter wavelength than visible light, and this allows electron microscopes to produce higher-resolution images than standard light microscopes. Electron microscopes can be used to examine not just whole cells, but also the subcellular structures such as organelles and compartments within them.

 

One limitation, however, is that electron microscopy samples must be placed under a vacuum in electron microscopy (and typically are prepared via an extensive fixation process). This means that live cells cannot be imaged.

In the image above, you can compare how Salmonella bacteria look in a light micrograph (left) versus an image taken with an electron microscope (right). The bacteria show up as tiny purple dots in the light microscope image, whereas in the electron micrograph, you can clearly see their shape and surface texture, as well as details of the human cells they’re trying to invade.

 

There are two major types of electron microscopy. In scanning electron microscopy (SEM), a beam of electrons moves back and forth across the surface of a cell or tissue, creating a detailed image of the 3D surface. This type of microscopy was used to take the image of the Salmonella bacteria shown at right, above.

 

In transmission electron microscopy (TEM), in contrast, the sample is cut into extremely thin slices (for instance, using a diamond cutting edge) before imaging, and the electron beam passes through the slice rather than skimming over its surface. TEM is often used to obtain detailed images of the internal structures of cells.

 

Electron microscopes are significantly bulkier and more expensive than standard light microscopes, perhaps not surprisingly given the subatomic particles they have to handle!

 

(Above information was adapted from Khan Academy: https://www.khanacademy.org/science/biology/structure-of-a-cell/introduction-to-cells/a/microscopy)

Please Note: Treat these microscopes with the greatest care!

 

Exercise 1: Basic Microscope Techniques

In this exercise, you will learn to use the microscope to examine a recognizable object, a slide of the letter e and crossed threads. Recall that microscopes vary, so you may have to omit steps that refer to features not available on your microscope. Practice adjusting your microscope to become proficient in locating a specimen, focusing clearly, and adjusting the light for the best contrast.

 

1. Obtain the following materials:

· Clear ruler  Blank slides  2 prepared slides: letter “e” & crossed thread

· Lens paper  Kimwipes®  Dropper bottle with distilled water

· Coverslips

 

2. Clean microscope lenses.

a. Each time you use the microscope, you should begin by cleaning the lenses. Using lens paper moistened with a drop of distilled water, wipe the ocular, objective, and condenser lenses. Wipe them again with a piece of dry lens paper.

 

3. Adjust the focus on your microscope:

a. Plug your microscope into the outlet.

b. Turn on the light. Adjust the light intensity to mid-range (if your microscope has that feature).

c. Rotate the 4X objective into position using the revolving nosepiece ring, not the objective itself.

d. Obtain the letter slide and wipe it with a Kimwipe® tissue.

i. Each time you study a prepared slide, you should first wipe it clean.

e. Place the letter slide on the stage and center it over the stage opening.

 

Please Note: Slides should be placed on and removed from the stage only when the 4X objective is in place. Removing a slide when the higher objectives are in position may scratch the lenses.

 

f. Look through the ocular and bring the letter into rough focus by slowly focusing upward using the coarse adjustments.

g. For binocular microscopes, looking through the oculars, move the oculars until you see only one image of the letter e. In this position, the oculars should be aligned with your pupils. In the margin of your lab paper, make a note of the interpupillary distance on the scale between the oculars.

h. Raise the condenser to its highest position, and fully close the iris diaphragm.

i. Looking through the ocular, slowly lower the condenser just until the graininess disappears. Slowly open the iris diaphragm just until the entire field of view is illuminated. This is the correct position for both the condenser and the iris diaphragm.

j. Rotate the 10X objective into position.

k. Look through the ocular and slowly focus upward with the coarse adjustment knob until the image is in rough focus. Sharpen the focus using the fine adjustment knob.

l. You can increase or decrease the contrast by adjusting the iris diaphragm opening.

m. Move the slide slowly to the right. In what direction does the image in the ocular move? _ Left _

n. Is the image in the ocular inverted relative to the specimen on stage? __Yes__

o. Center the specimen in the field of view; then rotate the 40X objective into position while watching from the side.

p. After the 40X objective is in place, focus using the fine adjustment knob.

q. The distance between the specimen and the objective lens is called the working distance. Is this distance greater with the 40X or the 10X objective? ___10X__

r. Compute the total magnification of the specimen being viewed. To do so, multiply the magnification of the ocular lens by that of the objective lens.

i. What is the total magnification of the letter as the microscope is now set? _400x__

 

Analysis Question 1

What would be the total magnification if the ocular was 20X and the objective was 100X (oil immersion)?

This is the magnification achieved by the best light microscopes.

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Total Magnification of a microscope can be calculated by multiplying the magnification of ocular and objective. So, 20 × 100 = 2000X

Therefore the total magnification will be 2000X.

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4. Measure the diameter of the field of view. Once you determined the size of the field of view for any combination of ocular and objective lenses, you can determine the size of any structure within that field. a. Rotate the 4X objective into position and remove the letter slide.

b. Place a clear ruler on the stage, and focus on its edge.

c. The distance between two lines on the ruler is 1 mm. What is the diameter (mm) of the field of view?

d. Convert this measurement to micrometers, a more commonly used unit of measurement in microscopy (1 mm=1,000 µm).

e. Measure the diameter for the field of view for the 10X and 40X objectives, and enter all three in the spaces below to be used for future reference.

 

4X = _ 4000Nm______ 10=__ 1000Nm_______ 40=__ 500Nm________

 

Analysis Question 2

What is the relationship between the size of the field of view and magnification?

As the magnification increases the field of view decreases (The field of view specifies how much of a specimen is visble in the eyepiece. Field of view and magnification are inversely related: the higher the magnification, the narrower the field of view, and vice-versa).

 

5. Determine spatial relationships. The depth of field is the thickness of the specimen that may be seen in focus at one time. Because the depth of focus is very short in the compound microscope, focus up and down to clearly view all the planes of a specimen.

a. Rotate the 4X objective into position and remove the ruler. Obtain the slide of crossed threads, wipe it with a Kim wipe, and place the slide on the stage. Center the slide so that the region where the two threads cross is in the center of the stage opening.

b. Focus on the region where the threads cross. Are both threads in focus at the same time? Yes

c. Rotate the 10X objective into position and focus on the cross. Are both threads in focus at the same time? Yes

 

Analysis Question 3

Does the 4X or the 10X objective have a shorter depth of field?

The 10X have a shorter depth of field because is zooms in more than the 4X that gives a larger depth of field.

 

d. Focus upward (move the stage up) with the coarse adjustment until both threads are just out of focus. Slowly focus down using the fine adjustment. Which thread comes into focus first? Is this thread lying under or over the other thread? Blue Over Red

e. Rotate the 40X objective into position and slowly focus up and down, using the fine adjustment only. Does the 10X or the 40X objective have a shorter depth of field? 40X has the shorter depth

 

 

Exercise 2: Viewing Prepared Slides

1. Using the Basic Microscope Techniques from Exercise 1, view a prepared slide of an Amoeba and one of a Paramecium.

a. Draw your field of view of each objective for each slide.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2. View a prepared slide of a cheek cell.

a. View the cells using the 4X and 40X objectives.

b. Draw your field of view for the 4X and 40X objectives.

c. Can you identify any organelles? If so, which ones? What is the function of the identified organelle(s)?

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Exercise 3: Preparing a Slide of Elodea 1. Prepare a wet mount.

a. Remove a leaf of Elodea.

b. Place the leaf onto a clean slide.

c. Add a drop of water to the leaf.

d. Place a coverslip over the leaf.

2. View the cells using the 4X and 40X objectives.

3. Draw your field of view for the 4X and 40X objectives.

4. Can you identify any organelles? If so, which ones? What is the function of the identified organelle(s)?

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Exercise 4: Proper Storage of the Microscope 1. Rotate the 4X objective into position.

2. Remove the slide from the stage.

3. Lower the stage all the way down.

4. Unplug the cord and wrap it around the base of the microscope.

5. Replace the dust cover.

6. Return the microscope to the cabinet using two hands; one hand should hold the arm, and the other should support the base.

7. These steps should be following every time you store the microscope.

8. Dispose of the Elodea slide according to the instructor’s directions.

9. Return all other materials to their original location.

 

Note: The results section of the lab report should include images from your field of view as well as answers to the questions asked throughout the exercises and the analysis questions.

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Week 5 Lab: Gene Expression

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Gene Expression Lab Simulation worksheet adapted by L. McPheron & Shannon Nixon; Phet Simulation by Elizabeth Hobbs; Mutation worksheet by Eliza Woo

Objectives:

● Identify the roles transcription factors, RNA polymerase, ribosomes, and mRNA destroyers have on transcription and translation.

● Distinguish between the location and function of regulatory regions compared to transcribed regions of DNA.

● Predict the effects of concentration, affinity, and degradation rates of transcription factors and RNA polymerase on gene expression.

● Identify the effects of mutations on gene expression. Background: Transcription​ is the process of making mRNA from DNA. This is a highly regulated process that our cells complete in preparation to make a protein. ​Translation​ is the process of making a protein from a piece of mRNA.

DNA ——————–> mRNA ——————–> protein transcription translation

Not all regions of DNA are used to make mRNA – only the parts of DNA that correspond to genes. Even then, not all gene regions are transcribed all the time. When genes are transcribed into mRNA depends on the needs of the cell. Once mRNA is made from DNA, it is translated into protein. Translation is an energy expensive process (it requires LOTS of ATP) which is one reason the cell only completes the process when the protein product is needed. This week’s “Reading and Lesson” explains many of the details of these highly complicated processes, transcription and translation. Please review the lesson for a deeper understanding of the concepts in this lab activity. Procedure: Click the Play arrow on this ​Gene Expression activity​ to complete the simulations. (The simulations are also embedded in the Canvas lab assignment page.) You will complete 3 simulations: 1) Expression, 2) mRNA, and 3) Multiple Cells.

Part 1: Expression Simulation

Click “Expression” to start that simulation. Notice the molecule that spans across the screen, from left to right. Answer the following 2 questions:

1. What is this molecule that spans across the page that is shown in red and blue?

2. What do you think the different colors (red and blue) of the molecule represent?

 

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https://phet.colorado.edu/en/simulation/gene-expression-essentials

 

 

Now, start the process of transcription.

For transcription, you need these things to happen. First, most genes require 1 or 2 “transcription factors” to bind to the area in front of the gene (called the “regulatory region”). Second, an RNA polymerase (an enzyme that makes mRNA from DNA) needs to be present in order for transcription to occur.

1. Drag one Positive Transcription Factor and one RNA Polymerase from the box called Biomolecule Toolbox to the regulatory region on the DNA molecule. This should start TRANSCRIPTION.

2. Now, drag a ribosome next to the mRNA, in order to do TRANSLATION. 3. The mRNA is eventually broken down by an mRNA destroyer protein. Drag one of these next to the

mRNA when it is done making a protein. 4. Put the protein in Your Protein Collection. 5. Stop the gene from working by dragging the Negative Transcription Factor to the Regulatory Area, and

remove the Positive Transcription Factor by dragging it out of the way.

After you have made 1 protein, answer these 5 questions. HINT: Think about what/where things are at the start, and what/ where things are at the end of the process.

1. What does the “Positive Transcription Factor” do?

 

 

2. What does the “RNA Polymerase” do?

 

3. What does the “Ribosome” do?

 

4. What does the “mRNA destroyer” do?

 

5. What does the “negative transcription” factor do?

 

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Click the yellow “Next Gene” box to begin working on the second gene. Can you remember the steps in order from your first trial? Try to see if you can! (HINT: There is one small difference between the transcription of gene 2 versus gene 1 – the difference is not in the order of steps but in the amount of something!) If not, not to worry, we are still learning… As a reminder, the steps are:

1. Drag Positive Transcription Factors and one RNA Polymerase from the box called Biomolecule Toolbox to the regulatory region on the DNA molecule. This should start TRANSCRIPTION!

2. Now, drag a ribosome next to the mRNA, in order to do TRANSLATION! 3. The mRNA is eventually broken down by an mRNA destroyer protein. Drag one of these next to the

mRNA when it is done making a protein. 4. Put the protein in Your Protein Collection. 5. Stop the gene from working by dragging the Negative Transcription Factor to the Regulatory Area, and

remove the Positive Transcription Factors by dragging them out of the way.

After you have made the second protein, answer these 2 questions.

1. What is one difference you noticed that was required to initiate the transcription of gene 2 versus gene 1?

2. What could be an advantage of multiple positive transcription factors versus only one?

 

 

Now, put all of your items back in the Biomolecule Toolbox and begin again, and answer the following 2 questions.

1. What happens if you add 2 RNA Polymerases (one after the first, before transcription is complete), and then 2 ribosomes (one for each mRNA)?

 

 

2. What would be the benefit of working this way versus adding RNA Polymerase one at a time?

 

 

Click the yellow “Next Gene” box to begin working on the third gene. Can you remember the steps in order from your first trial? Try to see if you can!

 

 

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Additional 4 Questions from the Expression Simulation:

1. What is gene expression?

 

 

2. What molecules are involved in gene expression? List them all and state the role of each.

 

 

 

 

 

 

3. What is the difference between the “regulatory region” and the “transcribed region”?

 

 

4. A student says that “ALL DNA codes for proteins.” Do you agree with her? Why or why not? Give evidence to support your answer.

Part 2: mRNA Simulation

At the bottom of the simulation page, click on the next simulation (it’s greyed out) called mRNA.

You should see a strand of DNA with a bunch of RNA Polymerases floating around. (If the RNA Polymerases are not moving, click the Play button.) Answer the following 7 questions.

1. Is mRNA being made?

 

2. In the Positive Transcription Factor box, slide the Concentration slider from NONE to just a tad (a couple millimeters or so) away from NONE. What do you notice is happening in the simulation now?

 

 

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3. Move the Concentration slider all the way to HIGH. How does this affect what is happening in the simulation?

 

 

4. Leave the Concentration slider on HIGH but move the Affinity slider all the way to LOW. What happens? Move the Affinity slider to a midway setting? What happens now? Based on these observations, what do you think ​affinity​ means in this simulation?

 

 

 

 

 

 

5. Place both sliders in the Positive Transcription Factor box on the HIGH setting. ​Predict ​what will happen to the simulation if you were to move the RNA Polymerase affinity slider to the LOW position. Record your prediction.

 

 

 

6. Now, move the RNA Polymerase affinity slider to the LOW position and record your observations. Was your prediction correct?

 

7. Place all the sliders in the HIGH position. Check the box to add Negative Transcription Factors and place the concentration and affinity sliders on HIGH. How does this change transcription compared to without Negative Transcription Factors?

 

 

 

Continue to play around with the sliders until you can accurately predict how the change will affect transcription each time.

 

 

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Additional 3 Questions from the mRNA Simulation:

1. What circumstances make the most mRNA? (What slider positions?)

2. What circumstances make the least mRNA? (What slider positions?)

 

3. Why would a cell need the option to make or not make a protein?

 

 

 

 

Part 3: Multiple Cells Simulation

At the bottom of the simulation page, click on the next simulation (it’s greyed out) called Multiple Cells.

Watch the generation of the graph called Average Protein Level vs. Time when one cell is working. If the graph does not automatically begin, then click the Play button at the bottom of the page. Answer the following 4 questions.

1. On the right side of the page, there are controls for Concentration, Affinity, and Degradation. (You need to click the green + to see the sliders.) Predict where you need to place each of the 3 sliders to achieve lots of protein. Record your predictions here:

a. The Concentration slider should be on LOW or on HIGH to achieve lots of protein?

 

b. The Affinity slider should be on LOW or on HIGH to achieve lots of protein?

 

c. The Degradation slider should be on LOW or on HIGH to achieve lots of protein?

 

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2. Now, move the sliders into the positions you predicted to see if your predictions were correct. (NOTE: Each time you click “Refresh” to restart the graph, all of the sliders reset themselves to their original setting.) Then, explain why each setting – concentration, affinity, and degradation – makes sense for making lots of protein.

 

 

3. Why would a protein need to be degraded?

 

 

 

4. Think back to last week’s lab – Lactase Enzyme Lab. Give an example from that lab of a time when it would be necessary to make a lot of one type of protein.

 

Part 4: Effects of Mutations on Gene Expression You have learned this week that cells use the two-step process of transcription and translation to transform a protein-coding DNA sequence into a chain of amino acids that makes up a protein. The resulting chain of amino acids will fold into a three-dimensional protein structure that defines the phenotype. Imagine that the following DNA sequence is part of a protein-coding gene. Use this sequence to answer the questions that follow.

… G G A T G C C G C T C T G C A A C T A C…

A) What is the ​complementary DNA sequence​ to the DNA sequence above? ​Hint: look back to your reading and lesson notes to recall the pairing rules for nucleotides A, T, G, and C if you need to!

 

 

B) What is the ​mRNA sequence​ transcribed from the DNA sequence from ​Part A​? ​Hint: your answer below should start with the letter ​G​ and not ​C​!

 

 

C) What ​corresponding amino acid sequence​ is translated from the mRNA sequence from ​Part (B)​? Use the genetic code from the lesson or the one posted in the lab. ​Remember that your amino acid sequence should always start with the ​START codon​!

 

D) For the following scenarios (i)-(iii), identify the type of mutation that has occurred (single base-pair substitution or frameshift mutation) to our original sequence AND the new amino acid chain that results

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from such a mutation. Complete the same sequence from complementary DNA sequence, then mRNA sequence, and then corresponding amino acid sequence like what you did in Parts A, B, and C above!

(i) The 4​th​ C in the original sequence is mutated to a T:

… G G A T G C C G C T ​T​ T G C A A C T A C …

Type of mutation:

New amino acid chain:

 

(ii) An extra C is inserted into the original sequence:

… G G A T G C C G C ​C​ T C T G C A A C T A C …

Type of mutation:

New amino acid chain:

 

(iii) The 5​th​ C in the original sequence is mutated to A:

… G G A T G C C G C T C T G ​A​ A A C T A C …

 

Type of mutation:

New amino acid chain:

 

E) At the end of translation, an amino acid chain will subsequently fold into a protein with a specific structure and function.

 

(i) Of the three mutations described in part (D), which mutation will cause the ​least ​change to protein function? Briefly explain your reasoning.

 

(ii) Which mutation would you expect to significantly alter protein function? Briefly explain your reasoning.

 

 

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Lab 5 – Meiosis

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Lab 5 – Meiosis

Before you begin your work, please read very carefully the Introduction in the Lab Manual and study Figure 2 closely. Then answer the two pre-lab questions as thoughtfully and in depth as you can.

Experiment 1: Following Chromosomal DNA Movement through Meiosis

(a) Part 1: You will simulate meiosis with two pairs of homologous chromosomes by using snap beads (they are in your kit). Then follow the instructions by simulating meiosis I and meiosis II. You may either photograph each stage and paste it into Part I – Meiotic Division Beads Diagram, or, you may draw each stage directly onto the lab page. Be sure to use two different colors.

(b) Part 2: This time, you will begin again with two sets of homologous chromosomes, but then make crossing-over happen for each set. Following that, you will then go through meiosis I and II again and draw, or photograph, each step carefully. You need to write down the number of chromosomes for each cell and stage in Part 1 and Part 2. – Explain the differences in outcome between Part 1 and Part 2.

You will find several questions at the end of experiment 1; please answer them all. You should remember that each and every species has different numbers of chromosomes. For example, humans have 23 pairs, that is, 46 total number of chromosomes. Mice have 40 chromosomes, dogs have 78, giraffes have 30, and some plants have over 200 chromosomes. The number of chromosomes found in the cells of individualspecies, are the result of their individual evolutionary history.

Experiment 2: The Importance of Cell Cycle Control

This will allow you to do some real-life research based on karyotypes. When you formulate your hypothesis please remember that it should be a brief, reasonable statement of expected outcomes. Please copy and paste five actual and complete karyotypes. Then answer the questions carefully.

  • Your Full Name:

    UMUC Biology 102/103

    Lab 5: Meiosis

    INSTRUCTIONS:

     

    · On your own and without assistance, complete this Lab 5 Answer Sheet electronically and submit it via the Assignments Folder by the date listed in the Course Schedule (under Syllabus).

    · To conduct your laboratory exercises, use the Laboratory Manual located under Course Content. Read the introduction and the directions for each exercise/experiment carefully before completing the exercises/experiments and answering the questions.

    · Save your Lab 5 Answer Sheet in the following format: LastName_Lab5 (e.g., Smith_Lab5).

    · You should submit your document as a Word (.doc or .docx) or Rich Text Format (.rtf) file for best compatibility.

     

    Pre-Lab Questions

    1. Compare and contrast mitosis and meiosis.

     

     

     

    2. What major event occurs during interphase?

     

     

     

    Experiment 1: Following Chromosomal DNA Movement through Meiosis

    Data Tables and Post-Lab Assessment

    Trial 1 – Meiotic Division Without Crossing Over Beads Diagram:

    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. Please use the lowest resolution possible so that your file does not become too large to submit.

    Insert pictures here:

     

    Prophase I

    Metaphase I

    Anaphase I

    Telophase I

    Prophase II

    Metaphase II

    Anaphase II

    Telophase I

    Cytokinesis

    Trial 2 – Meiotic Division with Crossing Over Beads Diagram:

    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.  Please use the lowest resolution possible so that your file does not become too large to submit.

    Insert pictures here:

     

    Prophase I

    Metaphase I

    Anaphase I

    Telophase I

    Prophase II

    Metaphase II

    Anaphase II

    Telophase I

    Cytokinesis

     

    Post-Lab Questions

     

    1. What is the ploidy of the DNA at the end of meiosis I? What about at the end of meiosis II?

     

     

     

    2. How are meiosis I and meiosis II different?

     

     

     

    3. Why do you use non-sister chromatids to demonstrate crossing over?

     

     

     

    4. What combinations of alleles could result from a crossover between BD and bd chromosomes?

     

     

    5. How many chromosomes were present when meiosis I started?

     

     

     

    6. How many nuclei are present at the end of meiosis II? How many chromosomes are in each?

     

     

     

    7. Identify two ways that meiosis contributes to genetic recombination.

     

     

     

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

     

     

     

    9. Blue whales have 44 chromosomes in every cell. Determine how many chromosomes you would expect to find in the following:

     

    i. Sperm Cell:

     

    ii. Egg Cell:

     

    iii. Daughter Cell from Mitosis:

     

    iv. Daughter Cell from Meiosis II:

     

    10. Research and find a disease that is caused by chromosomal mutations. When does the mutation occur? What chromosomes are affected? What are the consequences?

     

     

     

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

     

    Experiment 2: The Importance of Cell Cycle Control

    For each of the five abnormalities you find online, copy and paste a picture of it (and be sure to cite the URL for the picture)—you will not be photographing your own results for this section of lab, because you’re doing your research online for the questions below.

    Data Tables and Post-Lab Assessment

    1.  [paste in your online picture and cite the URL]

     

     

    2.  [paste in your online picture and cite the URL]

     

     

    3.  [paste in your online picture and cite the URL]

     

     

    4.  [paste in your online picture and cite the URL]

     

     

    5. [paste in your online picture and cite the URL]

     

     

    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.

     

     

     

    4. Why do cells which lack cell cycle control exhibit karyotypes which look physically different than cells with normal cell cycle.

     

     

     

    5. What are HeLa cells? Why are HeLa cells appropriate for this experiment?

     

    © eScience Labs, LLC 2014

Decondensed chromatin is located within the

/in /by

Question 1 of 48

3.75 Points

Decondensed chromatin is located within the

A.nucleolus during maintenance

B.nucleus during cell maintenance

C.nucleus during cell division

D.nucleolus during cell division  Reset Selection

 

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Question 2 of 48

3.75 Points

The evil arch-villain Dr. Black Thumb has created a new plant pathogen. The microbe has an enzyme allowing it to quickly convert β 1-4 glycosidic linkages to α 1-4 glycosidic linkages in a whole field of plants. If Dr. Black Thumb’s plan is not thwarted, crop harvests could be ruined due to

A.amylose and amylopectin becoming hard and inedible.

B.plant starches becoming rigid and popping cell membranes.

C.

plants flopping over.

D.polysaccharides converting into monosaccharides.      Reset Selection

 

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Question 3 of 48

3.75 Points

An atom with an atomic mass of 89 and an atomic number of 39 has how many

neutrons?

A.128

B.2

C.50

D.59      Reset Selection

 

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Question 4 of 48

3.75 Points

What factors allow a pool of 20 amino acids to produce thousands of unique proteins? (Select all that apply.)

A. variation in length of amino acid backbone

B. each protein is encoded by a distinct gene

C. variation in tertiary structure

D. variations in which amino acids are used

E. variations in glycosidic linkage

F. variations in the type of peptide bond

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Question 5 of 48

3.75 Points

_________________ prevent material from moving in or out of the brain’s capillaries

A.Desmosomes

B.Plasmodesmatas

C.Gap junctions

D.Tight junctions              Reset Selection

 

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Question 6 of 48

3.75 Points

Cardiac muscle requires junctions that allow electrical signals through. Cardiac muscle also relies on calcium to contract. What junction is involved and what organelle stores calcium?

A.desmosomes, smooth ER

B.plasmodesmata, rough ER

C.gap, smooth ER

D.tight, rough ER              Reset Selection

 

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Question 7 of 48

3.75 Points

The building blocks of nucleic acids are

A.sugars.

B.nucleotides.

C.peptides.

D.nitrogenous bases.     Reset Selection

 

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Question 8 of 48

3.75 Points

Which statements describe sodium atoms? Select all that apply.

A. forms cations

B. closest to the left side of the periodic table

C. easily forms covalent bonds

D. contains 1 valence electron

E. has 2 electrons in the first energy level

F. can lose one electron easily

G. outer energy level is stable

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Question 9 of 48

3.75 Points

If an integrin protein is mutated what cell function might be affected?

A.communication between cytoskeleton and proteglycan

B.fluidity of phospholipids

C.cellular motility

D.cytoplasmic communication    Reset Selection

 

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Question 10 of 48

3.75 Points

Buffers are important for doing experiments in labs, but they are not relevant to living systems.

True

False

Reset Selection

 

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Question 11 of 48

3.75 Points

The cell theory states

A.all cells will contain DNA, all cells are the smallest living things that can divide and all organisms are composed of cells

B.all organisms are composed of multiple cells, all cells arise spontaneously and all cells require nutrients

C.all cells are the smallest living things, all organisms are composed of one or more cells and all cells arise spontaneously

D.all organisms are composed of one or more cells, all cells are the smallest living things and all cells arise from other cells                Reset Selection

 

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Question 12 of 48

3.75 Points

Hiking in the snowy woods, you peek inside a cave and encounter a hibernating grizzly bear! Its metabolic rate seems to be very low. What do you predict is the predominant type of reaction occurring in this bear?

A.fatty acid anabolism

B.carbohydrate catabolism

C.carbohydrate anabolism

D.fatty acid catabolism  Reset Selection

 

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Question 13 of 48

3.75 Points

Rosenberg, a chemist, was observing the effects of an electric field on bacterial growth. He observed that bacteria stopped dividing when in an electric field. This research led to the anti-cancer drug cisplatin, a platinum containing compound. Rosenberg’s discovery was an example of

science.

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Question 14 of 48

3.75 Points

Enzymes are catalysts in reactions. What statements describe functions of enzymes? Select all that apply.

A. Enzymes are specific in their actions.

B. Once an enzyme binds to a substrate, it cannot be used again.

C. Enzymes lower the energy of activation needed for a reaction

D. Enzymes change the amount of free energy produced

E. Enzyme activity can be affected by temperature.

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Question 15 of 48

3.75 Points

In biological macromolecules like proteins, the hydrophobic residues tend to clump together in the interior of the folded structure. What is the best explanation for why this occurs?

A.Polar residues tend to bind to water in the cytoplasm as well as to each other. The water and polar residues cannot bind to the hydrophobic ones, so in the lowest energy state the hydrophobic residues are pushed together in the middle.

B.Protein folding machinery interprets the amino acid code to pack hydrophobic residues into the center of proteins. This process must be important, because the cell expends large amounts of ATP to precisely coordinate protein folding.

C.Hydrophobic residues bind to each other in specific ways. For instance, Ala forms di-methyl bonds, and phenylalanine binds isoleucine. This creates a tightly bound hydrophobic inner core.

D.Hydrophobic residues bind each other, while polar residues cannot bind each other. Therefore the hydrophobic ones end up stuck to each other in the core of the protein.    Reset Selection

 

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Question 16 of 48

3.75 Points

If two solutions are different, the one will the higher concentration of solutes is

A.isotonic

B.hypertonic

C.hypotonic        Reset Selection

 

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Question 17 of 48

3.75 Points

You are designing a museum exhibit to teach people about cells. In the entrance to the exhibit, visitors riding a moving walkway under flashing lights will gradually “shrink” down in size. To create this illusion, visitors will pass giant models of various biological parts, accompanied by scale bars.

Match each model to the appropriate scale bar to go with it.

A. 1 μm

B. 1nm

C. 10μm

D. 1cm

E. 1m

F. 0.1 nm

1. Carbon atom

2. cell nucleus

3. DNA molecule (10bp)

4. human being

5. human eyeball

6. skin cell

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Question 18 of 48

3.75 Points

The fluid mosaic model describes membranes as fluid due to

A.phospholipids sporadically placed throughout the membrane

B.the membrane is mostly composed of water

C.the proteins and the phospholipids can move laterally throughout the membrane

D.higher amounts of cholesterol

E.higher amounts of cholesterol               Reset Selection

 

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Question 19 of 48

3.75 Points

Cholera kills over 100,000 people each year worldwide due to diarrhea. The cholera toxin opens the CFTR chloride channel in the intestines, so that sufferers lose chloride, sodium and massive amounts of water.

On the other hand, the same CFTR channel is mutated in cystic fibrosis patients. With activity too LOW, they lack chloride flow and mucus builds up in the lungs.

This illustrates the importance of precise control of channel opening, known as

____________regulation.

A.gated

B.ungated

C.passive             Reset Selection

 

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Question 20 of 48

3.75 Points

When viewing the shape of a human cheek cell, what microscope would most likely be used?

A.light

B.dissecting

C.transmission electron

D.scanning electron        Reset Selection

 

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Question 21 of 48

3.75 Points

At a meal, you are served a hamburger with cheese, onions, and beef on a bun. What ingredients represent the most carbohydrates? Select all that apply.

A. beef

B. bun

C. onion

D. cheese

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Question 22 of 48

3.75 Points

Estrogen and testosterone are structurally related to cholesterol. Based on what you have learned about cholesterol, predict how these steroid hormones signal to the cell.

A.They are phagocytosed, degraded, and then released into the cell.

B.They make the membrane so fluid that small pores appear, allowing them to pass through.

C.They diffuse directly through the plasma membrane and into the cell.

D.They bind to receptors on the outside of the membrane, which then activate an intracellular signaling cascade.                Reset Selection

 

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Question 23 of 48

3.75 Points

Noncompetitive inhibition occurs when

A.a substance binds at the activity site

B.a substance binds on a site away from the active site

C.denaturing an enzyme

D.increasing the activity of an enzyme   Reset Selection

 

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Question 24 of 48

3.75 Points

Organisms must use macromolecules that have properties to match their functional requirements. In the list below, choose the appropriate macromolecule whose properties meet the requirement.

A. glycogen

B. RNA

C. DNA

D. cellulose

E. starch

1. Requirement:

Strong cell walls

 

Properties:

Linear polymer rigid and strong

2. Requirement

Stable storage of information

 

Properties:

4 base pairs, not easily hydrolyzed

3. Requirement:

Energy storage for seeds

Properties:

Energy-rich polysaccharides

4. Requirement:

Short-term energy storage (animals)

Properties:

Energy-rich polysaccharide

5. Requirement:

Transient transmission of information

Properties:

4 base pairs, easily hydrolyzed

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Question 25 of 48

3.75 Points

Membrane proteins are able to cross because sections are composed of

A.nonpolar phosphate regions

B.hydrophilic amino acids.

C.hydrophobic amino acids

D.polar amino acids

E.hydrophilic phosphate regions               Reset Selection

 

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Question 26 of 48

3.75 Points

The shape of the cell is predominantly maintained by the

A.plasma membrane

B.cytoskeleton

C.cytoplasm

D.endomembrane system           Reset Selection

 

Mark for Review What’s This?

Question 27 of 48

3.75 Points

What is the function of cholesterol in plasma membranes?

A.allows ions to pass

B.regulates pH

C.promotesartherosclerosis

D.regulates fluidity          Reset Selection

 

Mark for Review What’s This?

Question 28 of 48

3.75 Points

When donating blood, hemoglobin levels are measured by using a narrow glass tube to obtain blood from a finger prick. The blood is pulled up the tube by _____________________.

A.cohesiveness

B.covalent bonds

C.hydrophobic interactions

D.hydrogen bonds

E.ionic bonds     Reset Selection

 

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Question 29 of 48

3.75 Points

What protein is matched with its function?

A.aquaporins – move water through the membrane by active transport

B.carrier protein – nonspecific and will allow material to pass directly through

C.channel protein – allow passage of material through the hydrophilic pore

D.transport proteins – allow passage of material with the aid of ATP

 

Reset Selection

 

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Question 30 of 48

3.75 Points

C6H12O6 + 6O2 à 6H2O + 6CO2 is an example of ________________.

 

A.catabolism

B.anabolism

C.synthesis         Reset Selection

 

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Question 31 of 48

3.75 Points

Carbon-12, Carbon-13, and Carbon-14 are examples of

 

A.isomers

B.molecules

C.ions

D.isotopes

E.enantiomers  Reset Selection

 

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Question 32 of 48

3.75 Points

What statement(s) describes a concentration gradient?

A. Oxygen in blood plasma is .31 per 100 ml. Oxygen carried with hemoglobin is .69 per 100 ml.

B. Extracellular fluid contains 13.5 mmol of calcium, and 9 mmol of calcium is in the plasma.

C. The temperature inside the car is 39 degrees Celsius and the temperature outside the care is 39 degree Celsius.

D. Red blood cells cytoplasm contains a 0.9% salt solution. The extracellular fluid is 1.0%.

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Question 33 of 48

3.75 Points

How can ice float?

A.the covalent bonds expand, decreasing density

B.the hydrogen bonds expand, decreasing density

C.the covalent bonds collapse, increasing density

D.the hydrogen bonds collapse, increasing density          Reset Selection

 

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Question 34 of 48

3.75 Points

Which of the following form the foundation of plasma membranes?

A.Glycoproteins

B.Fatty acids

C.Glycolipids

D.Phospholipids

E.Proteins           Reset Selection

 

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Question 35 of 48

3.75 Points

You and your roommate are grocery shopping. “I don’t get it,” she says. “My doctor said I should buy this special milk because I don’t digest it well. But this brand says ‘lactose-free’ and this brand says ‘lactase added’ – which do I want?”

You reply: “The

_______________ is a sugar in milk that you have trouble digesting, and

_________________ is an enzyme that will digest it for you.

A.lactase, lactose

B.lactose,lactase              Reset Selection

 

Mark for Review What’s This?

Question 36 of 48

3.75 Points

If sodium does not move down its gradient in the co-transport pump, what would be the outcome?

A.Sugar would not be affected

B.Sugar would not be able to move down the gradient

C.Sugar would not be able to move up the gradient         Reset Selection

 

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Question 37 of 48

3.75 Points

When phospholipids are placed in water, why does a bilayer form?

A.Phospholipids are naturally attracted to each other, forcing phosphate heads to face the aqueous areas.

B.The fatty acid tails are forced together away from the water, and water can create hydrogen bonds with the phosphate heads.

C.Lipids are hydrophilic and will from hydrogen bonds with the water, forcing the hydrophobic heads towards the middle of the bilayer.

D.The polar tails will be attracted to the water and the nonpolar heads will be attracted to each other.   Reset Selection

 

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Question 38 of 48

3.75 Points

To break chemical bonds to start a chemical reaction, ___________ energy is needed.

A.kinetic

B.potential

C.activation

D.free   Reset Selection

 

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Question 39 of 48

3.75 Points

The microbiologist Louis Pasteur invented pasteurization, created vaccines for anthrax and rabies, and helped explain the germ theory of disease. He is often quoted as saying, “Chance favors the prepared mind.” A more accurate translation from the French, however, is “Where observation is concerned, chance favors only the prepared mind.” What can you conclude about Pasteur’s attitude about the role of chance in scientific discovery?

A.He thought that chance events are only useful if someone is intelligent enough to understand what happened.

B.He thought that observation of something unique doesn’t do any good if the scientist is not prepared to interpret and follow up on the chance discovery, due to a habit of studious work.

C.He thought you would have to be lucky to notice a chance event.

D.He thought that chance is the main determinant of who is successful in science, so all you can do is hope you get lucky.                Reset Selection

 

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Question 40 of 48

3.75 Points

A tarantula has eight legs, an arachnid in the order Araneae. A grass spider has eight legs, an arachnid in the order Araneaa. A mouse spider has eight legs, an arachnid in the order Araneae. There is a pattern. All organisms in this order have eight legs. This is

 

reasoning

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Question 41 of 48

3.75 Points

In a chocolate bar with nuts and caramel, there are 12 grams of fat, 33 grams of carbohydrates and 4 grams of protein. What percentage of calories comes from fat?

A.6.5%

B.19%

C.53%

D.41      Reset Selection

 

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Question 42 of 48

3.75 Points

Normal (homeostatic) pH level of blood serum’s pH is around 7.4. Carbonic acid is released in the blood to help maintain a pH that has high hydroxyl levels. This would cause pH to change from

A.basic to acidic

B.basic to neutral

C.neutral to basic

D.acidic to 7.4

E.basic to 7.4      Reset Selection

 

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Question 43 of 48

3.75 Points

What is the pathway in which a protein moves through the endomembrane system?

A.rough ER, Golgi apparatus, smooth ER, transport vesicle, plasma membrane

B.plasma membrane, transport vesicle, Golgi apparatus, rough ER

C.rough ER, Golgi apparatus, transport vesicle, plasma membrane

D.smooth ER, Golgi apparatus, transport vesicle, plasma membrane        Reset Selection

 

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Question 44 of 48

3.75 Points

Molecules move from a high to low concentration in

A.isotonic solutions

B.hypotonic solutions

C.hypertonic solutions

D.diffusion

E.osmosis            Reset Selection

 

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Question 45 of 48

3.75 Points

What examples describe the second law of thermodynamics? Select all that apply.

A. A penny will fall when you pick it up and let it drop.

B. A frying pan is on a hot stove. When removed it will cool.

C. Ice cubes will melt in a warm room.

D. Donuts nutrients are used to help you exercise.

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Question 46 of 48

3.75 Points

 

Researchers are working to develop biofuels to free us from dependence on fossil fuels. Based on what you know about cellulose, what do you predict are the major advantage and disadvantage of using cellulose-rich plant material as biofuel?

A.There is not much energy in the glycosidic bonds of cellulose, but at least there is a lot of it.

B.There is not much energy in the peptide bonds of cellulose, but at least it is very easy to break down

C.The breakdown of cellulose into fructose is an endergonic reaction, but an enzyme can reverse the equilibrium.

D.Cellulose is very difficult to break down into glucose, but it contains a lot of energy.    Reset Selection

 

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Question 47 of 48

3.75 Points

The impermeability of cell plasma membranes is a major barrier to using drugs to kill tumor cells or affect cells transgenically. CPPs are peptides that were discovered to have the ability to transport themselves (and even attached cargo) into cells. How they get into cells is still a mystery, but CPPs all have multiple positively charged groups. Which of the following membrane components are they most likely to be interacting with?

A.cholesterol

B.intrinsic membrane proteins

C.phospholipid heads

D.phospholipid tails        Reset Selection

 

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Question 48 of 48

3.75 Points

Which of the following is an example of an aliphatic hydrocarbon?

A.Benzene

B.Estrogen

C.Cholesterol

 

D.Methane