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Pre-Lab Questions Describe at least three similarities and three differences between mitosis and meiosis. The three similarities between mitosis and meiosis are: They both are types of cell division, both require spindle fibers, and both have duplication of chromosomes. The three differences between mitosis and meiosis are: Mitosis is one stage, but meiosis is two stages, Mitosis makes two daughter cells & meiosis makes four daughter cells, and Mitosis has diploid cells & meiosis has haploid cells. What major events occur during interphase? G1: Cell grows and performs normal functions S: DNA replication G2: cell undergoes last minute growth and organelle duplication. What are chromosomes made of? DNA coiled tightly around histones (structure supporting protein) Cancer is a disease related to uncontrolled cell division. Do a web-search to learn about chemotherapy drugs used to treat cancer. Briefly describe how one of these drugs functions in relation to cell division. Explain your answer. Include references to information sources used. Chemotherapy drugs travel through the bloodstream and target cells that are dividing into two new cells. The drugs do this to avoid replicating and spreading of foreign cancer cells. Unfortunately, chemotherapy drugs do not know exactly which cells to target, so they target our body’s normal cells too. This explains why your hair, skin and bone marrow is affected because these cells are always renewing themselves. tosis and Meiosis Predictions for Part 2: Table 2: Mitosis Data Stage Number of Cells in Stage Total Number of Cells Number of Hours Spent in Stage Interphase 87 100 87% Prophase 7 100 7% Metaphase 1 100 1% Anaphase 2 100 2% Telophase 2 100 2% Cytokinesis 1 100 1% Post-Lab Questions What is your conclusion after observing and counting the cells in the onion root tip? Did the results support your hypothesis? What, if anything, surprised you about the results? After observing the onion root tip, most of the cells were in interphase which did support my hypothesis. There were no surprises about the results since there is a large amount of cell growth in interphase. What stage were most of the onion root tip cells in? What stage as least common among the cells you looked at? Explain how the number of cells in each phase relates to the time it takes a cell to complete each phase. Most of the onion root tip cells were in interphase. The least common stages of mitosis that I observed were tied between anaphase, telophase, and cytokinesis with only one cell of each in that phase. I did not observe any in metaphase, and only two in prophase. Label the arrows in the slide image below with the appropriate stage of the cell cycle. 37033206141720Anaphase 0Anaphase 20574006553200Prophase 0Prophase 13162926863699Telophase 0Telophase 3886200129540Prophase 0Prophase 1987464411192Metaphase 0Metaphase 113538099060Interphase 0Interphase 0161925A B C D E F 00A B C D E F 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 when cells divide? As a cell increases in size, its ratio of its volume to surface area decreases. Like a balloon, a cell can only expand so much, mitosis allows to produce identical daughter cells and can carry out its functions normally. What steps occur during interphase that prepare a cell for division? During interphase, there are three major parts that are responsible for the first cellular growth with the increased amounts of cytosol within the cell i.e. production of protein, synthesis of DNA, production of more proteins to package the DNA. The last part of interphase synthesizes the protein, the cell continues to increase the size and the duplicate organelles. What would happen if mitosis were uncontrolled? Uncontrolled mitosis could lead to disease like cancer. Cancer is a disease of mutated cells that replicate at an unregulated or uncontrolled rate and form a tumor. Discuss one observation that you found interesting while looking at the onion root tip cells. One observation that I found interesting was the variety of different stages of the cells within the same tissues. I think part of me thought they would replicate in a synchronized manner. Mitosis and Meiosis Experiment 2: Following Chromosomal DNA Movement through Mitosis Post-Lab Questions Why are chromosomes important? What information do they provide? Chromosomes contain the genetic information for an organism. Without the correct number of chromosomes, cells would not function properly (ex: down syndrome). How many chromosomes did each of the daughter cells in your experiment contain at the end of mitosis? Each daughter cells received four chromosomes. Compare the initial cell with one of the daughter cells (after cytokinesis). Are there any differences? The daughter cells contain half the number of chromosomes as the initial cell. This makes the daughter cells haploid and initial cells diploid. How often do human skin cells divide? Why might that be? Compare this rate to how frequently human neurons divide. What do you notice? Human skin cells divide roughly every 2-4 weeks, assuming no injury has occurred. Human neurons divide only once and remain in the resting phase until death. The difference between the two is that human cells go through a lot because they are a barrier from the outside world. When they get damaged, new cells are created. Human neurons do not divide like this because their purpose is to store information from early development. Experiment 3: Following Chromosomal DNA Movement through Meiosis Post-Lab Questions Are the cells at the end of meiosis I haploid or diploid? Are the cells at the end of meiosis II haploid or diploid? Meiosis I: diploid Meiosis II: haploid Describe at least two ways meiosis I and meiosis II are different? Meiosis I separate homologous chromosomes and meiosis II separates sister chromatids. Meiosis I produce 2 diploid daughter cells and meiosis II produces 4 haploid daughter cells. How does crossing over affect the genetic content in the daughter cells? Crossing over creates genes that were not shown in either of the parent cells. How many chromosomes were present in the cell when meiosis I started in your bead experiment? 46 chromosomes How many cells are present at the end of meiosis II in your experiment? How many chromosomes are present in each cell? There were 4 cells. There were 23 chromosomes in each cell. What are two ways that meiosis contributes to genetic recombination? Crossing over Independent assortment of alleles Why is it necessary to reduce the number of chromosomes in gametes, but not in other cells? The number of chromosomes would double in the next division and continue doubling. Elephants have 56 chromosomes in every cell. Determine how many chromosomes you would expect to find in the following: Sperm Cell: 23 Egg Cell: 23 Daughter Cell from Mitosis: 23 Daughter Cell from Meiosis II: 23 Research and find a disease that is caused by chromosomal mutations. When does the mutation occur? What chromosomes are affected? What are the consequences? Down syndrome is a disease caused by chromosomal mutations. The extra 21st chromosome is added during fetal development. The 21st chromosome is affected. The consequences are delayed development, learning disabilities, and short stature. If you started with a cell with four chromosomes, what would happen if sexual reproduction took place for four generations using diploid (2n) cells instead of haploid cells (n)? (In other words, how many chromosomes would the cells have after four generations without meiosis?). 32 chromosomes Mitosis and Meiosis Experiment 5: The Importance of Cell Cycle Controls Post-Lab Questions Record your hypothesis from Step 1 in the Procedure section here: If someone were to be treated with the cancer fighting drugs, then it would be less likely for their offspring to inherit cancer. Do the results from the web-search support your original hypothesis? Why or why not? Cancer-fighting drugs along will not help in preventing the inheritance of cancer, but preventative screenings for those who might at risk can be very effective. Suppose a person developed a mutation in a somatic cell which diminishes the performance of the body’s natural cell cycle control proteins. This mutation resulted in cancer but was effectively treated with a cocktail of cancer-fighting drugs. Is it possible for this person’s future children to inherit this cancer-causing mutation? Be specific when you explain why or why not. Somatic cells do not form gametes, so there would be no chance of the child inheriting the mutation. Do cells which lack normal cell cycle control (cancerous cells) exhibit karyotypes that look physically different than cells with normal cell cycle control? They exhibit physically different karyotypes because the normal regulations that would prevent the cell from replicating when they shouldn’t be either not functioning properly or absent. Since, the cell cycle cannot be interrupted, the mutated cell exhibits the physically different appearance. What are HeLa cells? Why are HeLa cells appropriate for this experiment? Include references to information sources used to research HeLa cells. HeLa cells are a type of immortal cell line that is typically used in research. HeLa cells are used a lot in developing vaccines and nuclear testing. It would be fitting for this experiment because they could be used to test the different types of cancer fighting cells. Cite: The Embryo Project Encyclopedia. HeLa Cell Line | The Embryo Project Encyclopedia. (n.d.). Retrieved October 25, 2021, from https://embryo.asu.edu/pages/hela-cell-line. Research the function of the protein called p53. What does this function do? Explain how it can affect cell cycle control. Include references to information sources used. P35 functions as a neuron specific activator of cyclin-dependent is effective in when the development of the central nervous system is functioning. What is the Philadelphia chromosome? How is this chromosome related to cancer? Identify how this chromosome appears physically different in a karyotype than it appears in a normal karyotype. Include references to information sources used. The Philadelphia chromosome is the one that is an abnormally short 22nd chromosome and is involved in the translocation of 9th chromosome. It is also associated with the chromosomal abnormalities that cause chronic myeloid leukemia. Cite: MedicineNet. (2021, June 3). Medical definition of Philadelphia chromosome (ph). MedicineNet. Retrieved October 25, 2021, from https://www.medicinenet.com/philadelphia_chromosome_ph/definition.htm. Lab
