Mitosis and Meiosis Lab

Mitosis and Meiosis PRE-LAB QUESTIONS 1. What are chromosomes made of? a. Chromosomes are each made of protein and a single molecule of deoxyribonucleic acid (DNA) 2. Compare and contrast mitosis and meiosis. a. Mitosis i. 4 stages, purpose is cellular proliferation, produces 2 diploid daughter cells, chromosome number remains the same, genetic variation does not change b. Meiosis i. 8 stages, happens in germ cells. purpose is sexual reproduction, produces 4 haploid daughter cells, chromosome number is halved in each daughter cell, genetic variation is increased c. Both i. Produce new cells, similar basic steps, start with a single parent cell 3. How does mitosis differ in plant cells versus animal cells? a. The daughter cells separate differently during cytokinesis. animal cells form cleavage that gives way to formation of daughter cells. Due to their rigid cell wall, plant cells don't form cleavage. Mitosis and Meiosis 4. Cancer is a disease related to uncontrolled cell division. Investigate two known causes for cancer and use this knowledge to invent a drug that would prevent the growth of cancer cells. a. A known cause is mutation for cancerous cells that can result in the cell becoming overwhelmed with toxins due to a poor ATP generation. This can eventually infiltrate the nucleus and corrupt the DNA. b. A second cause is a weakened immune system from other factors such as bacteria, which can result in the body becoming unable to filter out malicious agents which results in an excess of toxins. c. The drug that I would invent would be an immune system booster to force the body to fight cancer cells. Mitosis and Meiosis EXPERIMENT 1: OBSERVATION OF MITOSIS IN A PLANT CELL Data Tables Table 1: Mitosis Predictions Interphase-20 hours Prophase-2 hours Metaphase- 30 minds Anaphase- 1 hour Telophase- 30 minutes Predictions Supporting Evidence I’ve learned that in fact, interphase is the longest phase and can last from 18-24 hours. Therefore, all the other processes have to fit into the remaining time. Table 2: Mitosis Data Image Stage Number of Cells in Stage Total Number of Cells Calculated % of Time Spent in Stage Interphase 20 20 53% Prophase 10 10 26% Metaphase 3 3 8% Anaphase 2 2 5% Telophase 1 1 3% Cytokinesis 2 2 5% Mitosis and Meiosis Table 3: Stage Drawings Cell Stage Drawing *d Interphase Prophase Metaphase Anaphase Telophase Cytokinesis Post-Lab Questions 1. Label the arrows in the slide image with the appropriate stage of the cell cycle. Mitosis and Meiosis A interphase_________ B telophase__________ Mitosis and Meiosis C interphase___________ D interphase_________ E prophase_ __________ F anaphase ___________ 2. In what stage were most of the onion root tip cells? Does this make sense? a. Interphase is the phase that takes the longest and cells spend most of their lives in it. Yes it makes sense. 3. As a cell grows, what happens to its surface area-to-volume ratio (hint: think of a balloon being blown up)? How does this ratio change with respect to cell division? a. As a cell is preparing for division, the cells get larger, but also the less surface area it will have for its size. As it gets bigger, the outside of the cell is unable to keep up with the needs of the inside. 4. What would happen if mitosis were uncontrolled? a. If mitosis were uncontrolled, a group of cells would form and become a tumor which could also become cancerous. 5. How accurate were your time predictions for each stage of the cell cycle? a. My time predictions were similar but surprisingly not as close as I expected. 6. Discuss one observation you found interesting while looking at the onion root tip cells. a. I found it interesting that the prophase was so confusing. I then learned that there is an early prophase stage as well as a later stage, which looks a bit different. Mitosis and Meiosis E0XPERIMENT 2: FOLLOWING CHROMOSOMAL DNA MOVEMENT THROUGH MITOSIS Cell Cycle Division: Mitosis Beads Diagram Prophase: During this phase, the chromatids and the set of replicated chromosomes are lines up beside each other horizontally. The sister chromatids have 20 beads each, 5 beads on each of the four strands. The xXXx replicated chromosomes had 12 beads each, 3 beads on each of the 4 strands Metaphase: The sister chromatids: and the replicated chromosomes line up in a vertical line being tugged on by the spindles which keeps them aligned. x x X X Anaphase: The chromatid strands pull apart from each other to opposite sides of the cell. Telophase: Two brand new nuclei form around the chromatid strands Cytokinesis: Now there are two cells, the cytoplasm is completely separating from one another. Mitosis and Meiosis Post-Lab Questions 1. Why are chromosomes important? What information do they provide? a. They are important because they contain the entire genetic information for an organism. The organism’s DNA is contained within the chromosome. 2. How many chromosomes did each of your daughter cells contain? a. Each daughter cell contained two chromosomes 3. How often do human skin cells divide? Why might that be? Compare this rate to how frequently human neurons divide. Is there a difference? Why might that be? a. Human skin cell divides once a day. The cell cycle is shorter, which means that they go through mitosis more frequently. Human neuron cells spend decade in interphase instead of dividing. Mitosis and Meiosis EXPERIMENT 3: FOLLOWING CHROMOSOMAL DNA MOVEMENT THROUGH MEIOSIS Cell Cycle Division: Part 1 – Meiotic Bead Diagrams (Without Crossing Over) Prophase I: Nuclear membrane disappears, the centrioles and spindle fibers appear. Homologous chromosomes pair to form tetrads Metaphase I: Chromosomes line up at the metaphase plate between the spindle fibers. Anaphase I: Tetrads pull apart to opposite poles Telophase I: Cell starts pinching inward forming cleavage to form two different cells. Prophase II: Chromosomes are condensing nuclear membrane disappears. Centrioles and spindle fibers Mitosis and Meiosis reappear Metaphase II: Chromosomes line up in the middle with the spindle fibers attaching to the centromeres. Anaphase II: Chromatids get pulled to opposite poles by spindle fibers. Telophase II: The nuclear membranes starts to reappear, pinching inward to form cleavage for four new cells. Cell Cycle Division: Part 2 – Meiotic Bead Diagrams (With Crossing Over) Prophase I: One chromosome from mother one from father come together and wrap around each other so closely that portions of one switch with portions of the other. They are also lined up along the middle. Metaphase I: Also lined up vertically in the Mitosis and Meiosis middle, depending on which side the chromosomes line up, will determine what gene goes to what egg. Anaphase I: Spindles branch from the chromosomes and pull them apart to opposite sides of the cell. Telophase I: Two new nuclei begin to form around the chromosomes. Prophase II: Chromosomes condense again nuclear membrane disappears. Metaphase II: The chromosomes line up again in the middle (metaphase plate) Anaphase II: The chromosomes are split in half and move to the side will Mitosis and Meiosis Telophase II: 4 new nuclei are formed around the chromosomes Post-Lab Questions 1. What is the state of DNA at the end of meiosis I? What about at the end of meiosis II? a. In meiosis I the result is two diploid cells that contain the same amount of DNA as the original parent cell. At the end of meiosis II, four haploid cells are the result 2. Why are chromosomes important? a. They are important because they contain the entire genetic information for an organism. The organism’s DNA is contained within the chromosome. 3. How are meiosis I and meiosis II different? a. In meiosis I, homologous chromosomes separate, while in meiosis II, sister chromatids separate. Meiosis II produces 4 haploid daughter cells, but meiosis I produces 2 diploid daughter cells. Crossing over only occurs in meiosis I 4. Why do you use non-sister chromatids to demonstrate crossing over? a. You use non-sister chromatids to demonstrate crossover because sister chromatids are identical, therefore there would be no change in genetic make up of the daughter nucleus. Mitosis and Meiosis 5. What combination of alleles could result from a crossover between BD and bd chromosomes? a. The combination of alleles that could result from crossover between BD and bd chromosomes are Bb, Db, Bd and Db. 6. How many nuclei are present at the end of meiosis II? How many chromosomes are in each? a. There were four nuclei present at the end of meiosis II, and two chromosomes in each. Identify two ways that meiosis contributes to genetic recombination. 7. Why is it necessary to reduce the number of chromosomes in gametes? a. Without the reduction, the union of two gametes during fertilization would result in offspring with twice the normal number of chromosomes 8. Blue whales have 44 chromosomes in every cell. Determine how many chromosomes you would expect to find in the following: a. Sperm Cell: 22 chromosomes b. Egg Cell: 22 chromosomes c. Daughter Cell from Mitosis: 44 chromosomes d. Daughter Cell from Meiosis II: 22 chromosomes 9. Research and find a disease that is caused by chromosomal mutations. When does the mutation occur? What chromosomes are affected? What are the consequences? Mitosis and Meiosis a. A common genetic disorder is down syndrome. This happens when the person had three copies of chromosome 21 instead of two copies. It is caused by abnormal cell division during the development of the sperm cell or egg cell. 10. Diagram what would happen if sexual reproduction took place for four generations using diploid (2n) cells. a. The zygote would not be able to develop. If an animal were to have more than the standard number of chromosomes, it would be fatal. Polyploid cells are only normal in plants. Mitosis and Meiosis EXPERIMENT 4: CROSSING OVER Data Tables Table 4: Sodaria fimicola Crossover Data Image Number of Crossovers Number of NonCrossovers Image 1 8 6 Image 2 3 20 Image 3 4 9 Post-Lab Questions 1. Determine the percentage of crossovers. To do this, divide the number of crossovers by the total number, and multiply it by 100. a. 20% 2. Determine the map distance. To do this, divide the percentage of crossover by two. Note that the number is divided by two because crossover occurs once between two chromosomes. a. 10 Mitosis and Meiosis EXPERIMENT 5: THE IMPORTANCE OF CELL CYCLE CONTROL Data Mitosis and Meiosis 1. With Patau’s syndrome, there is an additional chromosome 13 2. There is an extra X chromosome in the karyotype with Klinefelter’s syndrome. 3. There is an extra 18th chromosome in Edward’s syndrome. 4. A segment of chromosome 9 is reversed or flipped in the patient with advanced ovarian cancer. 5. In the karyotype with metastatic melanoma, the person has so many excess chromosomes especially for chromosomes 2 and 7. Post-Lab Questions 1. Record your hypothesis from Step 1 here. a. The karyotype of cancerous cells is abnormal due to the mutations in the DNA. The cell division that occurs in the cancerous cells is similar to the normal cell Mitosis and Meiosis division. The only difference lies in the check points. The cancerous cells skip the checkpoints where the errors are checked. 2. What do your results indicate about cell cycle control? a. Cell cycle regulates the timing and accuracy of cell division process. Cancer cells have mutated cell cycle control gene, which will allow them to divide faster and often uncontrolled. The loss of cell cycle control leads to increased number of chromosomes. In the karyotypes I found, there were clear indications of mutations. 3. Suppose a person developed a mutation in a somatic cell that diminishes the performance of the cell’s natural cell cycle control proteins. This mutation resulted in cancer but was effectively treated. Is it possible for this person’s future children to inherit this cancer-causing mutation? Why or why not? a. Yes, they could inherit the same mutation. This does not establish the cause of the mutation; there may be a strong connection between the genetic predisposition and environmental causes, resulting in a mutation. In this case even if the mutation is not transmitted directly through reproduction, genes facilitated by the mutation can be transmitted, resulting in the same situation to offspring 4. Why do cells that lack cell cycle control exhibit karyotypes that look physically different than cells with normal cell cycle control? a. They are different because some of the karyotypes have different form of dysfunction as the result of the loss in the control of the cell cycle. 5. What are HeLa cells? Why are HeLa cells appropriate for this experiment? a. HeLa cells are able to survive outside the body into a lab environment, providing a never-ending test for cellular development. For this reason, they are appropriate for study related to mutated cells and karyotypes Mitosis and Meiosis 6. Research the function of the protein p53. Explain how changes in p53 activity may affect cell cycle control. a. P53 is responsible for cellular integrity. The main function is to prevent mutant cells. It helps with the process of mapping proteins correctly and sending them to the correct location. 7. What is the Philadelphia chromosome? How is this chromosome related to cancer? Identify how this chromosome appears physically different on a karyotype than it appears on a karyotype of normal chromosomes. a. It’s an abnormality on the chromosome 22. Part of chromosome 9 has been transposed. It can be found majority of myelogenous leukemia. The karyotype appears physically different in size; it is smaller than the normal chromosome 22.