1. Lab 5 Mitosis and Meiosis<br />Materials:<br />Pop-beads, string, zip lock bag, microscope, onion root prepared slide<br />Hypothesis: Predict how the cells division differs during mitosis and meiosis <br />Objectives:<br />1. Identify the phases of mitosis using pop-beads and observing plant cells.<br />2. Place the phases of mitosis and meiosis in proper sequence.<br />3. Explain the consequences of both mitosis and meiosis.<br />Background Info:<br />I. MITOSIS<br />A: Pop-Bead Activity<br />Pop-beads are small, colored beads that can be joined together to simulate chromosome strands. We will use the pop-it beads to simulate the process that chromosomes undergo during cell division. We start with a cell with a chromosome number of 4 (4 chromosomes, or 2 homologous pairs). A homologous pair of chromosomes are two chromosomes of the same shape and size, one from the male parent and the other from the female parent. We will use red to identify the chromosome from the male parent and yellow for the chromosome from the female parent.<br />B: Microscope Activity<br />Most of the cells you will see on prepared slides of mitotic tissues will be in interphase, since this is the longest phase of the cell cycle. In this phase, DNA is being used to make protein and the DNA itself is replicated, so the chromosomes are loose and unwound and impossible to see even using a microscope. The chromosomes are not visible until the cells enter prophase, the first phase of mitosis. It will be possible to see condensed chromosomes in all four phases of mitosis. Keep in mind that the process of mitosis is continuous and the separations of the various stages are arbitrary. Many of the mitotic cells you see may be in some intermediate point between the phases you have learned about.<br />Procedure: <br />Mitosis:<br />1. Make 4 chromosomes: two long chromosomes (4 beads of same color each) and two short (2 same color beads each) chromosomes . The two long chromosomes should each have the same number of beads, as should the two short chromosomes. The two long chromosomes are one homologous pair; the two short chromosomes are the second homologous pair.<br />2. Replicate your chromosomes by making an identical set of pop-it bead chromosomes (you should have a total of eight pop-it bead strands; four long and four short). Attach the identical replicas (chromatids) by their magnetic centromeres (remember a centromere is the region of the chromosome where duplicated strands of a chromosome are attached). You are now ready to proceed with mitosis.<br />3. Move the “chromosomes” through each of the four stages of mitosis. Draw and label the popbead chromosomes for ONE of the phases in your data section of the lab write-up. (It is not necessary to draw each individual bead.)<br />1. Mitosis in Plant Cells: Prepared Slide of Onion Root Tip<br />Set up a compound light microscope and turn on the light. <br />Place a slide containing a stained preparation of the Allium (onion root tip). <br />Focus in on low power, and then switch to medium or high power. Below find micrographs of the four stages of mitosis. Use them to help you identify the stages on the microscope slide. <br />Now count the number of cells found in each stage of mitosis and place the data in the chart below. <br />Determine the percentage of time each cell will spend in each stage of mitosis. Divide the number of each cell by the total number of cells and multiply by 100 to determine the percentage. Place these values in the chart below. <br />II. MEIOSIS<br />A: Reviewing Meiosis<br />1. Pop-Bead Activity<br />Using your book as a guide and the 4 pop-bead chromosomes you created earlier, simulate each of the phases of meiosis in division I and division II. You should come away with a general idea of the process of meiosis I and meiosis II, and how these stages compare to mitosis.<br />1. Draw the chromosomes as they would appear during metaphase I of meiosis.<br />2. Draw the chromosomes as they would appear at the conclusion of telophase I.<br />3. Draw the chromosomes as they would appear at the end of telophase II<br />Microscope data:<br />Stage of MitosisNumber of CellsPercent of time in each stage =# of cells in stage X 100%Total # of CellProphase %Metaphase %Anaphase %Telophase %Interphase (Not a Mitotic Stage) %Total # cells 100%<br />Line graph the data you have just collected. Be sure to label the X and Y axis & include the units of measurement. <br />Title: __________________________________________________<br />Graph Legend:<br /> <br />Analysis:<br />1. The life cycle of a cell consists of interphase and four phases of mitosis. In which part of the life<br />cycle does a cell spend most time?<br />2. What data or observations did you acquire during the lab to support your answer?<br />3. Why can’t you see chromosomes in cells during interphase?<br />4. Why can’t you see a nucleus in cells during cell division?<br />5. Describe at least three major differences between metaphase in mitosis and metaphase I in meiosis?<br />6. How does the number of human chromosomes before and after mitosis compare to the number of<br />chromosomes before and after meiosis?<br />Conclusion:<br />Write summary of lab, any possible sources of error and was the lab successful for you?<br />