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Comparing Mitosis and Meiosis The body carries out two types of cell division. Mitosis results in the formation of new body cells, called somatic cells. The cells that are formed by mitosis are genetically the same as each other and the same as the parent cell. Somatic cells contain chromosomes in pairs called homologues. Homologous chromosomes carry alleles for the same traits, but are not identical to one another. Each pair of homologous chromosomes is made up of one chromosome inherited from the mother, and the other from the father. Since somatic cells have pairs of chromosomes, they are described as being diploid cells. Meiosis results in the formation of reproductive cells called gametes. Gametes have one homologue of each pair found in the somatic cells; meiosis accomplishes the task of dividing the amount of DNA contained by the cell in half. Since they have a single copy of each type of chromosome, gametes are described as being haploid cells. At fertilization, haploid gametes fuse to create a diploid zygote. The developing offspring grows as somatic cells are produced through the process of mitosis. What You Will Do a) Model cell division processes. b) Compare the process of mitosis with the process of meiosis. c) Create diagrams of mitosis and meiosis to show the results of these processes. Materials cell templates ruler colored pencils or markers 4 pieces of yarn, 4 different colors scissors Prepare your materials Using the first color of yarn, cut two pieces 1.5 cm long. Cut two pieces of a second color 1.5 cm long. Using a third color, cut two pieces 2.5 cm long. Cut two pieces of a fourth color 2.5 cm long. Part A: Mitosis • Use diagrams A, B, and C for this part of the activity. Place them on the table, one below the other in the proper order. • Diagram A represents the parent cell during interphase. Place two long pieces of yarn of different colors and two short pieces of yarn of different colors in the cell. These are the four chromosomes contained in the parent cell. There are two homologous pairs: the two long chromosomes make up one pair, the two short chromosomes are another pair. Note that the paired chromosomes are not identical. • Draw the chromosomes in cell A at the top of the mitosis column. Before the cell begins mitosis, chromosomes are copied using a process called replication. • To show DNA replication, match new pieces of yarn identical to those in the parent cell. The matched pieces of yarn represent sister chromatids. • Sketch cell A as it appears now below the first sketch. During mitosis, sister chromatids line up in the center of the cell. • Transfer the chromosomes to diagram B and position them within the dashed outlines. • Draw the chromosomes in cell B. • Anaphase separates sister chromatids. Move the chromosomes that are lined up on the left to the left. Move the chromosomes on the right to the right side of the cell. • Draw the chromosomes in cell B as they appear now. Once the chromosomes separate, the cell pinches in half to form two new cells. • Move the chromosomes on the left side of diagram B to the left cell of diagram C, and those on the right side of B to the right cell of diagram C. • Draw the chromosomes in the C cells. Part B: Meiosis • Use diagrams D, E, F and G for this part of the activity. Place them on the table, one below the other in the proper order. • Diagram D represents the parent cell before meiosis begins. Place two long pieces of yarn of different colors and two short pieces of yarn of different colors in the cell. These are the four chromosomes contained in the parent cell. Note that this cell is the same as the parent cell in part A. • Draw the chromosomes in cell D at the top of the meiosis column. Before the cell begins meiosis, DNA replication occurs. • To show replication, match new pieces of yarn identical to those in the cell to represent sister chromatids. • Draw the chromosomes in cell D as they appear now below the first sketch. Sister chromatids line up in the center of the cell in homologous pairs. These groups of chromosomes are called tetrads. • Transfer the chromosomes to diagram E and position them within the dashed outlines. • Draw the chromosomes in cell E. • Anaphase I separates homologous chromosomes, but the sister chromatids do not split. Move the sister chromatids that are lined up on the left to the left. Move the chromatids on the right to the right side of the cell. • Draw the chromosomes in cell E as they appear now. Once the homologous chromosomes separate, the cell pinches in half to form two new cells. • Move the sister chromatids on the left side of diagram E to the left cell of diagram F, and the sister chromatids on the right side of E to the right cell of diagram F. • Draw the chromosomes in the F cells. Sister chromatids line up in the center of each cell, the centromeres now break, and the chromosome copies separate. • Move the chromosomes that are lined up on the left to the left of the cells in diagram F. Move the chromosomes on the right to the right side of the cells. • Draw the chromosomes in the F cells as they appear now. The two cells pinch in half to form two new cells each for a total of four cells. • Move the chromosomes on the left side of diagram F to the left cells of diagram G, and those on the right side of F to the right cells of diagram G. • Draw the chromosomes in the G cells. Part C: Analysis Complete Table 1 on your handout. Answer the following on a separate sheet of notebook paper. 1. Compare the chromosomes of the parent cell for mitosis to those of the parent cell for meiosis. 2. Compare the chromosomes of one daughter cell produced by mitosis to those of the parent cell. 3. Compare the chromosomes of one daughter cell produced by meiosis to those of the parent cell. 4. Look at metaphase of mitosis (3rd sketch down) and metaphase of meiosis I (3rd sketch down). How are they similar? How do they differ? 5. Look at metaphase of mitosis (3rd sketch down) and metaphase of meiosis II (5th sketch down). How are they similar? How do they differ? 6. Look at the sketches of the daughter cells of meiosis. How are they similar to one another? How do they differ? Complete Table 2 and Table 3 on your handout.