Lemoine Module 2 Lab 1 PDF

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BIOS 1010 General Biology Module 2 Lab 1

Cell Reproduction Maintaining the appropriate number of chromosomes requires special processes during cell division. We know these special processes as mitosis for production of body cells and meiosis for production of sex cells in animals and spores in plants.

Materials Pipe cleaners, beads, or other appropriate materials for making chromosomes.

Part 1. Visualization of Mitosis You will look at images of cells in an onion root tip to observe the process of mitosis.

Procedure 1. Go to the University of Arizona’s Biology Project website’s cell cycle page at

http://www.biology.arizona.edu/cell_bio/tutorials/cell_cycle/main.html 2. Read each page and click “next” when you are done with each page – you will read about the basics of DNA, as well as the cell cycle. Remember, animal cells go through the cell cycle and mitosis too, even though the tutorial is devoted to onion cells. 3. When you get to the page The Cell Cycle and Mitosis Tutorial, read each description and look at each cell photo carefully – then click “next.” 4. On the “Test Yourself” page, click “Problem 1.” After answering that question, write the correct answer on the worksheet, then click “Next.” 5. Continue answering the questions, writing the correct response on the worksheet, and clicking the next problem number after each answer. When you are finished with all 11 questions, click “The End.” 6. Before continuing with the Biology Project website, answer question 12 and make sketches of each stage of mitosis in the onion root tip table under Part 1 on the worksheet. Pictures of the stages of mitosis in an onion root tip are available for reference in the Cell Reproduction Online Lab PowerPoint. 7. On the web page that appears, click the hyperlink to Online Onion Root Tips.

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8. Carefully study each page, clicking “Next” to move on. 9. On the next page, there is a blank table for determining the length of time necessary for each portion of the cell cycle. You do not need to copy this table, as a similar one can be found on the worksheet. Identify each of the cells’ stage of the cell cycle (interphase or one of the 4 mitotic phases). When you have identified all 36 cells, fill in the table on the worksheet. To calculate the length of time an onion cell might spend in each of these phases, you must first calculate the proportion of cells in each phase. Simply take the number of cells in a particular phase (for example, if 4 of the 36 cells are in metaphase, divide 4 by 36, which equals 0.11). 10. When you have determined the proportion in each phase, calculate the length of time that phase should take. For simplicity’s sake, assume that the entire cell cycle takes 24 hours. If one phase includes .11 of the cells (from the example above), then multiply 24 by .11. This number (24 x .11 = approximately 2.6) means that this phase takes about 2.6 hours out of the total of 24 hours. These 5 numbers (one for each phase) should add up to 24 hours if you did the math correctly. You may be slightly off due to rounding. Complete the table using your calculations and answer the questions following the table on the worksheet.

Part 2. New Cells Mitosis Once sister chromatids are successfully separated, the rest of the cell contents are divided, but not necessarily equally. There are two typical outcomes in cytokinesis, depending on the size of the “daughter” cells. A. Fission Equal-sized daughter cells are the most common outcome of cell division. The cells examined in Part I were produced by this simple cytokinesis, as are the cells of an embryo. B. Budding Yeasts are examples of unicellular organisms that use cytokinesis to produce asymmetric cells, small ‘buds’ at the side of the parent cell. Each little cell eventually grows to the size of the parent, and it in turn may form a new bud. A colony of chained-together parents and buds may form over time.

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Procedure: 1. Look at the illustration and the picture of yeast cells budding in the Cell Reproduction Online Lab PowerPoint. 2. Sketch what you see on worksheet, labeling a parent cell and a bud.

Meiosis Ova and sperm are the products of meiosis. Sperm are the smallest animal cells (excluding the tail) and ova are among the largest.

Procedure 1. Look at the picture of a slide of an ovum in a mature follicle in the Cell Reproduction Online Lab PowerPoint. 2. Imagine how many of ova would be required to lie side-by-side in a line across the diameter of the field. Assume the picture shows the entire field of view of the microscope at the stated magnification. Diameter

3. Calculate the approximate width of an ovum by dividing the diameter of the field (determined in an earlier lab to be ~5 mm at 40x, ~2 mm at 100x, and ~0.5 mm at 400x)) by the number of cells you estimate are needed to fill that diameter. For example, in the field illustrated here, it appears Cell that the cell in view is about one-fourth of the diameter of the field. If we had measured the diameter of the field at 2 mm, the cell must be 2 mm ¸ 4 or 0.5 mm in diameter. 4. Record your estimation of the size of the ovum on the worksheet. 5. Repeat Steps 1 – 4 using the picture of a slide of sperm cells. Find the length of the sperm cell without the tail.

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Part 3. Simulation of mitosis and meiosis. Mitosis and meiosis are both processes that result in nuclear division. They are usually accompanied by cytokinesis and therefore result in new cells. Mitosis consists of one division and results in two identical daughter cells. Meiosis is a division of reduction. It results in four unique haploid daughter cells. In this simulation, you will assume your organism has four chromosomes.

Procedure. 1. Watch the following video showing a simulation of mitosis and meiosis. https://www.youtube.com/watch?v=zGVBAHAsjJM

2. Make four replicated chromosomes using pop beads, pipe cleaners, or other objects. Since we are using a diploid organism, it will have 2 of each kind of chromosome. We are using chromosomes from after replication of DNA so each will have two chromatids. Make the chromosomes so that you can differentiate them. One should be large and the other should be smaller. Make the homologous chromosomes different colors to represent the chromosomes from the mother and father. See the figure below to see what your chromosomes should look like.

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Cell Replication: Data, Observation, and Analysis Worksheet Name ____Joe Lemoine_______ Part 1. Cell Cycle and Mitosis

1. What difference can you see when you compare the nucleus of a dividing cell with that of a non-dividing cell? Chromosomes can be seen in the nucleus of the dividing cell because they are visible when the cell is dividing opposed to non-dividing cells.

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Onion root tips. Description and Observation

Make a simple sketch of an onion cell in this stage of mitosis

Prophase: Condensation of pairs of copied chromosomes

Metaphase: Organization of chromosomes at center of cel

Anaphase: Separation of sister chromatids

Telophase & Cytokinesis: Regrouping of chromosomes as 2 nuclei and Formation of 2 new cells

Length of time for parts of the cell cycle. Interphase (not part of

Prophase

Metaphase

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Anaphase

Telophase

Total

Number of cells Proportion of cells Time for each phase

mitosis) 20

10

3

2

1

36

.556

.27fi

.0fi3

.056

.02fi

1.0

17 hrs

3 hrs

2 hrs

1 hr

24 hours

Which phase of the cell cycle takes the longest? Interphase Which phase of mitosis takes the longest? prophase Why might this particular phase of mitosis take longer than the other phases? Prophase takes the longest because in this phase the cell prepares to divide by tightly condensing its chromosomes and initiates the spindle formation. The nucleolus also disappears during early prophase.

Part 2. New Cells Mitosis B. Budding

Sketch of yeast as seen under the microscope, Label a parent cell and a bud:

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Meiosis Ovum My estimate of the size of an ovum: .83mm (40x - .5mm)

Sperm My estimate of the size of a sperm (excluding the tail) : .36mm (400x = .5mm)

Part 3. Simulation of mitosis and meiosis. A. Paste your pictures of your mitosis simulation here. Label the stage in each picture.

i. prophase

ii. metaphase

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iii. anaphase

iv. telophase/cytokinesis B. Paste your pictures of your meiosis simulation here. Label the stage in each picture.

i. prophase I

ii. metaphase I

iii. anaphase I.

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iv. telophase/cytokinesis I

v. prophase II

vi. metaphase II.

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vii. anaphase II

viii. telophase/cytokinesis II

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