Life Science Online Lab Instructions: Mitosis and Meiosis Introduction Mitosis is an orderly process of DNA replication and separation to prepare the cell for division. Mitosis is used for embryo growth and cell repair. The process has been divided into separate phases. Typically, interphase lasts for at least 90% of the total time required for the cell cycle. However, the cells you will observe in this online lab are photos of specialized cells in fast-growing onion root-tips. More of their time needs to be spent in mitosis so they can divide faster and the root can grow faster. Therefore, since the main function of onion root-tip cells is accelerated growth and not other cell activities, onion root cells spend a smaller percent of the time during interphase than most other cells. If you want to use a real microscope and slide to do this lab, contact me and I can set up a time for you to come into the lab at school. It takes an onion cell approximately 24 hours to complete mitosis. We can easily calculate the amount of time that the cell spends in each phase. To do this, you divide the number of cells in a particular phase by the total number of cells. Then, you multiply this percentage by 24 hours to give the actual amount of time spent in each phase. For Example: 20 cells in interphase/25 cells total = 0.80 = 80% of all cells are in interphase. 0.80 x 24 hours = 19.2 hours Since the number of significant digits in the numbers involved in the calculations (20, 25 and 24) is 2, the result should also have two significant digits, so we round 19.2 to 19. Meiosis is a cell division process in which reproductive cells divide into gametes (eggs or sperm). While mitosis results in two identical cells with the same number of chromosomes of the original cell, meiosis results in 4 unique cells with half the chromosome number. The full chromosome number of a species is restored when a sperm fertilizes an egg and forms a zygote. The zygote undergoes mitosis to grow into an embryo and eventually an adult. Objectives ● Understand the process of mitosis ● Learn the differences between mitosis and meiosis Procedure 1. Print out a copy of the Lab Report so you have a table you can use to tally your results and enter your calculations. 2. Do the online mitosis lab at the following website, and tabulate the results you get: http://www.biology.arizona.edu/Cell_BIO/activities/cell_cycle/cell_cycle.html. 3. Answer the questions in the Lab Report. 4. Type up your work, and then upload your Lab Report for grading. 1 Jun 16
