BIO201 Lab 3

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Lab 3 Mitosis and Meiosis BIO201L Student Name: Ani Harutyunyan Access Code (located on the lid of your lab kit): AC-BX89CU Lab Report Format Expecta0ons U"lize college level grammar and professional forma4ng when comple"ng this worksheet. Submissions without proper forma4ng, all required photos or suﬃcient responses will be rejected. Pre- lab Ques>ons 1. What are chromosomes made of? Chromosomes, found within the nucleus of both animal and plant cells, are thread-like formaDons composed of protein and a single strand of DNA. 2. Compare and contrast mitosis and meiosis, ensuring to detail the differences in both funcDon and in process. ( Hint : Your response should be 4-5 sentences long.) Mitosis is a process of cell division that results in two geneDcally idenDcal daughter cells, each with the same diploid number of chromosomes as the parent cell. This means that the chromosome count remains unchanged during mitosis. In contrast, meiosis is a different type of cell division that leads to the producDon of four daughter cells, each with a haploid chromosome set. This halving of the chromosome number during meiosis is crucial for sexual reproducDon, ensuring that when gametes fuse, the resulDng offspring has the correct diploid number. Therefore, while mitosis maintains the chromosome number, meiosis reduces it by half in the resulDng cells. 3. Cancer is a disease related to uncontrolled cell division. InvesDgate two known causes for these rapidly dividing cells and use this knowledge to invent a drug that would inhibit the growth of cancer cells. ( Hint : Your response should be 4-5 sentences long.) Cancer is caused by uncontrolled cell division, and two known causes for this rapid division are mutaDons in affected cells and a weakened immune system. MutaDons in certain genes can lead to uncontrolled cell growth and division, while a weakened immune system fails to recognize and eliminate cancerous cells. To invent a drug that inhibits the growth of cancer cells, we can target these causes. One approach is to develop drugs that target specific mutaDons in cancer cells, prevenDng them from dividing uncontrollably. Another approach is to develop drugs that boost the immune system's ability to recognize and eliminate cancer cells. By targeDng these causes, we can potenDally develop effecDve drugs to inhibit the growth of cancer cells.

Lab 3 Mitosis and Meiosis BIO201L EXPERIMENT 1: OBSERVATION OF MITOSIS IN A PLANT CELL Introduc>on Ques>ons 1. State how you will calculate the number of hours each stage of mitosis takes based on observaDons. Do so by either staDng the “Hours of Stage” equaDon, or by discussing the equaDon and its applicaDon. If you decide to insert an equaDon, you must use an equaDon editor to properly state the equaDon with the correct symbols and fracDon format. To calculate the number of hours each stage of mitosis takes based on observaDons, you can use the following equaDon: 2. Here's how the equaDon works and its applicaDon: 1. Number of Cells in Stage : Count the number of cells in a specific stage of mitosis (e.g., prophase, metaphase, anaphase, or telophase). 2. Total Number of Cells Observed: Count the total number of cells observed in all stages of mitosis. 3. Total Time of Mitosis : This is the total duraDon of the mitoDc process, which is known or has been observed. By inserDng the values into the equaDon, you can calculate the duraDon of each stage of mitosis in hours. The fracDon represents the proporDon of cells in a specific stage relaDve to the total, and mulDplying this fracDon by the total Dme of mitosis gives the duraDon of that parDcular stage. 3. In Table 1, below, predict how many hours of the 24-hour cell cycle you think each step takes. Ensure you provide robust supporDng evidence to back your predicDon. Table 1: Mitosis Predic>ons Predic>ons I expect interphase to last around 20 hours and the enDre cell division process to span approximately 4 hours—encompassing 3 hours for prophase, 30 minutes for metaphase, and 20 minutes for anaphase. Suppor>ng Evidence Interphase, typically the lengthiest phase of the cell cycle, can extend up to 24 hours, and this is parDcularly evident in the onion root Dp, where the enDre cell cycle is known to last about the same duraDon. Therefore, it's reasonable to expect that interphase would dominate this period, possibly consuming around 20 hours.

Lab 3 Mitosis and Meiosis BIO201L Data and Observa>ons Record your observaDons in the table below. Based on those observaDons, calculate the percentage of Dme spent in each phase of mitosis. Table 2: Mitosis Data Chosen Image Onion Root Dp Stage Number of Cells in Stage Total Number of Cells Calculated % of Time Spent in Stage Interphase 20 25 80% Prophase 2 25 8% Metaphase 0 25 0% Anaphase 1 25 4% Telophase 1 25 4% Cytokinesis 1 25 4%

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Lab 3 Mitosis and Meiosis BIO201L Below, insert the drawings you generated of each phase of mitosis. You must include your handwriden name in the background. Submissions that do not meet this requirement will be rejected. Table 3: Stage Drawings Cell Stage Drawing Cell Stage Drawing Interphase Anaphase Prophase Telophase Metaphase Cytokinesis

Lab 3 Mitosis and Meiosis BIO201L Results and Discussion 1. Label the arrows in the slide image below with the appropriate stage of the cell cycle. A. Interphase B. telophase C. Interphase D. Interphase E. Prophase F. Anaphase

Lab 3 Mitosis and Meiosis BIO201L 2. What stage were most of the onion root Dp cells in? Based on this observaDon, explain why this is to be expected. Most cells in the onion root epidermis were noted to be in interphase, aligning with expectaDons given that interphase is the lengthiest phase of the cell cycle. 3. As a cell grows, what happens to its surface area : volume raDo? (Think of a balloon being blown up). How is this changing raDo related to cell division? During a cell's growth, there reaches a point where its surface area is insuﬃcient to support its volume, prompDng the need for cell division. As the cell enlarges, the surface area-to-volume raDo decreases. 4. What is the funcDon of mitosis in a cell that is about to divide? The goal is to guarantee that every daughter cell inherits an idenDcal copy of the DNA from the parent cell. 5. What would happen if mitosis were uncontrolled? Improper regulaDon of mitosis can disturb the natural progression of the cell cycle, leading to serious consequences for the organism. These can include the emergence of cancer, abnormal Dssue growth, chromosomal anomalies, and geneDc instability. 6. How accurate were your Dme predicDons for each stage of the cell cycle? Given that most cells were in the interphase stage, my esDmate of the Dme allocaDon proved to be quite precise. 7. Discuss one observaDon that you found interesDng while looking at the onion root Dp cells. I had assumed that cells would progress through the phases simultaneously, so it was intriguing to observe a significant number of cells moving through different stages independently.

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Lab 3 Mitosis and Meiosis BIO201L EXPERIMENT 2: TRACKING CHROMOSOMES THROUGH MITOSIS Introduc>on Ques>ons 1. Cite an example of a type of cell that undergoes mitosis. Why is it important for each daughter cell to contain informaDon idenDcal to the parent cell? Skin cells serve as an example of cells that replicate through mitosis to renew the epidermal layer. It's crucial for daughter cells to receive the same geneDc material to maintain the organism's integrity and avert dysfuncDons or illnesses. 2. Hypothesize what would happen if the sister chromaDds did not split equally during anaphase of mitosis. Should sister chromaDds not divide evenly during anaphase, the daughter cells produced would possess an atypical chromosome count, potenDally resulDng in geneDc imbalances and possibly triggering disorders or affecDng cellular funcDon. 3. Human skin cells divide at a higher rate than neurons (nerve cells). Hypothesize why this may be. Human skin cells divide more olen than neurons, probably due to their constant exposure to external factors and the need for regular regeneraDon. In contrast, neurons, which have a specialized communicaDon role, undergo cell division less frequently.

Lab 3 Mitosis and Meiosis BIO201L Data and Observa>ons Once you have completed the digital exercise, select the “Results Table” budon at the bodom right-hand corner of the screen and select the “Generate PDF” budon at the top of the following screen. Insert your download into this document by selecDng the Insert > Object > Text from file. Resize if necessary.

Lab 3 Mitosis and Meiosis BIO201L Results and Discussion 1. How many chromosomes were present before mitosis? 46 2. How many chromosomes did each of the daughter cells contain aler mitosis? 23 chromosomes

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Lab 3 Mitosis and Meiosis BIO201L EXPERIMENT 3: FOLLOWING CHROMOSOMAL DNA MOVEMENT THROUGH MEIOSIS Introduc>on Ques>ons 1. List two differences between meiosis I and meiosis II. 1. Chromosomal ReducDon: Meiosis I is a reducDonal division where homologous chromosomes are separated, halving the chromosome number. Meiosis II, on the other hand, is an equaDonal division where sister chromaDds are separated, maintaining the chromosome number. 2. GeneDc RecombinaDon: Meiosis I features crossing over and recombinaDon between homologous chromosomes, leading to geneDc diversity. In contrast, meiosis II does not involve such geneDc exchanges between sister chromaDds. 2. Why is it necessary to reduce the number of chromosomes in gametes, but not in other cells? In Meiosis I, homologous chromosomes undergo crossing over and recombinaDon, contribuDng to geneDc variability, while Meiosis II lacks these geneDc exchanges between chromaDds. 3. What is the ploidy of the daughter cells at the end of meiosis I? What about at the end of meiosis II? Halving the chromosome count in gametes is crucial so that upon fusion during ferDlizaDon, the offspring retain the appropriate chromosome number, preserving the species' chromosomal conDnuity.

Lab 3 Mitosis and Meiosis BIO201L Data and Observa>ons Once you have completed Part 1 of the digital exercise, take screenshots and insert them below. Resize if necessary. Table 5a (Meiosis I):

Lab 3 Mitosis and Meiosis BIO201L Table 5b (Meiosis II):

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Lab 3 Mitosis and Meiosis BIO201L Once you have completed parts 2, 3, and 4, select the “View Data Table” budon at the bodom lel-hand corner of the home screen. Review your table. If you would like to make any changes, select the “Return” budon in the bodom right-hand corner. If you are saDsfied with your answers, take a screenshot and insert it below. Resize if necessary:

Lab 3 Mitosis and Meiosis BIO201L Results and Discussion 1. How did crossing over affect the geneDc content in the gametes? Use your results to support your answer. In the process of crossing over, gametes swap chromosome segments with one another, giving rise to disDncDve geneDc configuraDons that differenDate them from surrounding gametes. EssenDally, crossing over guarantees that each resulDng cell possesses a unique geneDc makeup. 2. Based on your observaDons in the digital exercise, what can you conclude about the severity of nondisjuncDon that occurs in meiosis I as opposed to meiosis II? Abnormal chromosome counts can lead to disorders like Down syndrome, among others. Such anomalies are typically seen as harmful and represent a departure from the standard chromosomal composiDon. 3. Blue whales have 44 chromosomes in every cell. Determine how many chromosomes you would expect to find in the following: a. Sperm Cell: 22 b. Egg Cell: 22 c. Daughter Cell from Mitosis: 44 d. Daughter Cell from Meiosis II: 22

Lab 3 Mitosis and Meiosis BIO201L EXPERIMENT 4: THE IMPORTANCE OF CELL CYCLE CONTROL Introduc>on Ques>ons 1. In this experiment, you will review some of the karyotypic differences that can be observed when comparing normal, controlled cell growth and abnormal, uncontrolled cell growth. What is a karyotype? Give the definiDon below. A karyotype is the complete set of chromosomes in an organism, typically displayed as a visual profile of the individual chromosomes arranged and numbered by size and structure used for idenDfying chromosomal abnormaliDes and determining the chromosomal makeup of an individual. 2. Why do cells which lack cell cycle control exhibit karyotypes which look physically different from cells with normal cell cycle. Because the cell cycle acts as a controlling system, cells lacking appropriate regulaDon of this cycle exhibit diverse chromosomal arrangements. This is due to the fact that interference in the cell cycle can cause mistakes in the distribuDon of chromosomes during meiosis, modifying the geneDc makeup of the cells produced. 3. Record your hypothesis from Step 1 in the Procedure secDon here. There could be discrepancies in the number of chromosomes or anomalies in the structure of the chromosomes. 4. What are HeLa cells? Why are HeLa cells appropriate for this experiment? HeLa cells represent an everlasDng human cell line. This cell line is suitable because it permits endless experimentaDon.

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Lab 3 Mitosis and Meiosis BIO201L Data and Observa>ons 1. Below, write a paragraph or paragraphs that detail(s) the observaDons you made during your research. To earn credit, describe the images you viewed, where you obtained them, and the differences you noted between the normal and abnormal karyotypes. ( Hint : Your response must be thorough and will likely contain around 6-10 sentences.) You may include copies of the photos you reviewed, but these are not required for credit and will not be graded. Upon scruDnizing a series of karyotype images sourced from diverse channels and digital databases, I discerned the nuances between normal and abnormal chromosomal arrangements. A typical karyotype exhibits 46 chromosomes, paired and ordered by size with the sex chromosomes, X and Y, concluding the sequence. ContrasDngly, abnormal karyotypes unveiled a spectrum of chromosomal aberraDons. Trisomy, characterized by an extra chromosome, manifests in condiDons like Down syndrome, while monosomy, marked by a missing chromosome, is linked to Turner syndrome. TranslocaDons, the exchange of geneDc segments between non-homologous chromosomes, are implicated in diseases such as leukemia and lymphoma. DeleDons, the loss of chromosomal segments, underlie disorders like Prader-Willi and Angelman syndromes, whereas inversions, the rearrangement of geneDc material within a chromosome, are associated with Charcot-Marie-Tooth disease and Cornelia de Lange syndrome. IdenDfying dispariDes between normal and abnormal karyotypes olen hinges on meDculous chromosome comparisons. However, some aberraDons, such as the addiDonal chromosome 21 indicaDve of trisomy 21, are conspicuously evident. The analysis of karyotypes emerges as a pivotal tool for geneDc disorder diagnosis, allowing for the detecDon of chromosomal alteraDons that aid in deciphering paDent symptoms and tailoring precise treatment regimens.

Lab 3 Mitosis and Meiosis BIO201L Results and Discussion 1. What do your results indicate about cell cycle control? Certain syndromes might be passed down geneDcally, while others could arise from inadequate regulaDon of the cell cycle. 2. Research the funcDon of the protein called p53. What does this funcDon do? Explain how it can affect cell cycle control. The protein p53 is a tumor suppressor that regulates the cell cycle. It ensures DNA integrity by halDng the cell cycle for repair or triggering cell death if the damage is too severe. If p53 is mutated, this control is lost, potenDally leading to uncontrolled cell division and cancer. 3. What is the Philadelphia chromosome? How is this chromosome related to cancer? IdenDfy how this chromosome appears physically different on a karyotype than it appears on a karyotype of normal chromosomes. The Philadelphia chromosome is a result of a translocaDon, where parts of chromosomes 9 and 22 swap places. This abnormal chromosome is associated with certain types of leukemia. On a karyotype, it appears shorter than normal chromosome 22 due to the translocaDon. 4. Suppose a person developed a mutaDon in a somaDc cell which diminishes the performance of the body’s natural cell cycle control proteins. This mutaDon resulted in cancer, but was effecDvely treated with a cocktail of cancer-fighDng techniques. Is it possible for this person’s future children to inherit this cancer-causing mutaDon? Be specific when you explain why or why not. No, the future children of this person are not at risk of inheriDng the cancer-causing mutaDon. This is because the mutaDon occurred in somaDc cells, which are not involved in reproducDon. Only mutaDons in germ cells, which are the reproducDve cells, can be passed on to offspring.

BIO201 Lab 3

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