NextGen Biology Cohort___ Name________________________________________________Period___ Onion Root Tip Mitosis Lab Purpose To better understand the phases of the cell cycle and the important events in each phase. Part I. The Basics ONION ROOT TIP (low power) A B G I C E E D H F 1) Examine the diagram above right. Identify the phase of the cell cycle for each letter. interphase prophase Letter Phase metaphase A I P M A T C B I P M A T C C I P M A T C D I P M A T C E I P M A T C F I P M A T C G I P M A T C H I P M A T C I I P M A T C anaphase telophase How I identified it: 2) Why do you think the onion root tip is chosen to examine in this lab? cytokinesis Part II. Microscope Work 1) Under low power, locate the region of rapidly dividing cells on the prepared slide of the onion root tip as shown in the picture in the Pre-Lab. After locating the cells, switch to high power. 2) Locate cells that appear to be in various stages of mitosis. 3) Using a pencil, draw 4 cells undergoing any four different stages of mitosis. Then, describe the events occurring in that cell during that phase. Phase: _______________________________ Phase: _______________________________ Description of what occurs in the cell during that phase: Description of what occurs in the cell during that phase: Phase: _______________________________ Phase: _______________________________ Description of what occurs in the cell during that phase: Description of what occurs in the cell during that phase: Part III. Cell Cycle Activity You and a partner will classify each cell based on its stage of mitosis. Based on the number of cells found in each phase, you can approximate the amount of time cells spend in each stage. Use this link: http://bit.ly/onionrootonline Procedure 1) Identify the stages of mitosis for each cell. Once you identify the stage, click on the blue labeled stage of mitosis and the cell will go to the corresponding column. If you choose the incorrect stage, try again until the cell goes to the correct column. 2) Count the number of cells in each stage of mitosis and complete the following chart. 3) To calculate percentages should be rounded to 1 decimal place. 4) To calculate the amount of time spent in each stage: a) Convert the % of cells into a decimal (13.9% = 0 .139) b) Multiply this decimal by 24. This will give you the amount of hours spent in each stage. Round your calculated hours to 1 decimal place. Determine Interphase Prophase Metaphase Anaphase Telophase Total # of Cells 36 % of Cells 100% Amount of Time in Each Stage 24 hours Part IV. Post-Lab Questions 1) In which stage do cells spend the… a) most amount of time? _________________________ b) least amount of time? _________________________ 2) What are three reasons why mitosis is necessary in your body? ____________________________ ____________________________ ____________________________ 3) When a cell is in interphase… a) Is the DNA in the form of chromatin or chromosomes? ____________________________ b) Is the nuclear membrane present? ___________________________ c) In what substage (G1, S, or G2) is the DNA replicated? ___________________________ 4) At the end of prophase… a) Is the DNA in the form of chromatin or chromosomes? ___________________________ b) Is the nuclear membrane present?___________________________ 5) At the end of metaphase… a) Where is the DNA located in the cell? ___________________________ b) What brought the DNA to this location? ___________________________ c) Where do these structures attach to the DNA? ___________________________ 6) When a cell is in anaphase… a) What happens to the DNA? ___________________________ 7) At the end of telophase… a) Is the nuclear membrane present? ___________________________ b) Is the DNA in the form of chromatin or chromosomes? ___________________________ 8) When a cell finishes cytokinesis… a) Is the nuclear membrane present? ___________________________ b) Is the DNA in the form of chromatin or chromosomes? ___________________________ c) How many cells are present? ___________________________
