GB 1713 L11 Mitosis And Meiosis PDF

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Mitosis and Meiosis Pre-Lab Questions 1. Describe at least three similarities and three differences between mitosis and meiosis. Similarities: 1. Both types of cell division 2. Both require spindle fibers 3. Duplication of chromosomes Differences: 1. Mitosis is one stage, meiosis is two stages 2. Mitosis makes two daughter cells, meiosis makes four daughter cells 3. Mitosis has diploid cells and meiosis has haploid cells

2. 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

3. What are chromosomes made of? DNA coiled tightly around histones (structure supporting protein)

4. 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. Mitosis and Meiosis 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 bodies normal cells too. This explains why your hair, skin, and bone marrow is affected, because these cells are always renewing themselves.g https://www.cancerresearchuk.org/about-cancer/cancer-ingeneral/treatment/chemotherapy/how-chemotherapy-works

Experiment 1: Observation of Mitosis in a Plant Cell Data Tables Table 1: Stage Drawings

Cell Stage

Drawing

Interphase

Prophase

Metaphase

Anaphase

Telophase

Cytokinesis

Hypothesis for Part 2:

Table 2: Mitosis Data

Stage

Number of Cells in Stage

Total Number of Cells

Calculated % of Time Spent in Stage

Interphase

Prophase

Metaphase Anaphase Telophase Cytokinesis

Post-Lab Questions 1. 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? 1. Meiosis

2. 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.

3. Label the arrows in the slide image below with the appropriate stage of the cell cycle.

4. 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? The surface area to volume ratio decreases. In cell division, the surface area increases and the volume stays the same.

5. What steps occur during interphase that prepare a cell for division? Interphase can be divided into three different phases. The first phase is G1 where the growth continues. The next phase is S where DNA replication happens. The last phase is G2 where proteins are synthesized.

6. What would happen if mitosis were uncontrolled? Uncontrolled mitosis would cause a disruption in the number of chromosomes.

7. Discuss one observation that you found interesting while looking at the onion root tip cells. The chromosomes were very visible, especially during metaphase when the chromosomes are attaching to the spindle fibers. Mitosis and Meiosis

Experiment 2: Following Chromosomal DNA Movement through Mitosis Post-Lab Questions 1. 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)

2. How many chromosomes did each of the daughter cells in your experiment contain at the end of mitosis? Each daughter cell received four chromosomes.

3. 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 the initial cell diploid.

4. 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 occured. Human neurons divide only once and remain in the resting phase until death. The difference between the two is that human skin 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 1. 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: dipoid meiosis II: haploid

2. Describe at least two ways meiosis I and meiosis II are different? Meiosis I separates homologous chromosomes and meiosis II separates sister chromatids. Meiosis I produces 2 diploid daughter cells and Meiosis II produces 4 haploid daughter cells.

3. 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.

4. How many chromosomes were present in the cell when meiosis I started in your bead experiment? 46 chromosomes.

5. 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.

6. What are two ways that meiosis contributes to genetic recombination? a. Crossing over b. Independent assortment of alleles.

7. 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.

8. 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

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? 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.

10. 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...