Lab 9 Cell Division online Fall2020 (1) PDF

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Harper College Bio110—Introduction to Biology and Society Lab 9: Cell Division Name: ______________________________________________ Date: ___________ Objectives:  Compare and contrast the steps, functions, and end-products of mitosis and meiosis.  Describe the major events in each stage of mitosis and meiosis, as well as in cytokinesis.  Count the number of chromosomes on diagrams of cells during various stages of the cell cycle  Identify which stage of the cell cycle that cells spend the most time.  Identify the different stages of mitosis when provided with an image of a real or animated cell. Introduction: The capacity for cell division is an important characteristic of all living organisms, since it is essential to reproduction, development, growth, regeneration and wound healing. In some cell division processes, one cell divides to become two cells. The original cell is called the mother cell (or parent cell) and the two new cells formed are called the daughter cells. In unicellular prokaryotes, like bacteria, this cellular division process is called binary fission and is the main means of reproduction for these organisms. In eukaryotes, mitosis (nuclear division) coupled with cytokinesis (cytoplasmic division) is one of the main mechanisms for cell division. In unicelluar eukaryotes, like yeast or amoebas, mitosis with cytokinesis is used for asexual reproduction. In the multicellular organisms, like humans and plants, mitosis with cytokinesis is used for growth and development, repair of damaged tissues, and replacement of dead or wornout cells. In sexually reproducing multicellular eukaryotes, a second type of cell division occurs which divides a mother cell into four daughter cells. This process, when coupled with cytokinesis is called meiosis and it is responsible for producing the sperm and egg cells that are found in sexually reproducing organisms. When an egg is fertilized by sperm, this forms a zygote (or fertilized egg), which is the first cell of a multicellular eukaryote. This zygote will then divide by mitosis and cytokinesis to help to form numerous cells that make up the body of the multicellular organism. Exercise 1: Overview of mitosis and meiosis In eukaryotes, during the cell division process, there are two concurrent stages: (1) a division of the nucleus – called mitosis – and (2) a division of the cytoplasm – called cytokinesis. The resulting two daughter cells formed are precisely identical to each other and to the original mother cell in terms of genetic information carried on their chromosomes. These daughter cells retain the diploid number of chromosomes that was originally found in the mother cell. A. Background on Mitosis The process of mitosis and cytokinesis are continuous and neither the beginning nor the end of a stage can be sharply defined. The cell cycle includes interphase, mitosis, and cytokinesis. Mitosis can be further divided into easily distinguished stages known as prophase, metaphase, anaphase, and telophase.

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Go to the “Mitosis Mover!” activity at: https://biomanbio.com/HTML5GamesandLabs/Genegames/mitosismoverpage.html Click on “Start a New Game!” Click “OK!” to advance. You will not be able to go back to previous slides – it is recommended that you browse the following questions beforehand. This mitosis activity does not include details about the microtubules and mitotic spindle. Follow the instructions on the screen while also answering the questions below. 1. What 3 processes are included in the cell cycle? Interphase Mitosis cytokinesis 2. What happens during interphase? The cell does normal cell activities like making proteins 3. Fill in the blank: Uncoiled stringy DNA is called ___Chromatin _________. 4. Fill in the blank: __Mitosis________ is necessary for making more cells needed for growth, development, and tissue repair (healing). 5. Fill in the blank: Mitosis ultimately results in the formation of _ _2___ genetically identical daughter cells. 6. True or false: Mitosis is performed to make sperm or egg cells. ___ture______ 7. List the 4 phases of mitosis in order. Prophase Metaphase Anaphase Telophase 8. Fill in the blank: During prophase, chromosomes ___Condense________ and become visible. 9. Fill in the blank: Each condensed chromosome during prophase exist as two identical halves called _______ sister chromatids __________. 10. What happens to the nucleus during prophase? During prophase, the chromosomes condense, the nucleolus disappears, and the nuclear envelope breaks down. 11. What happens during metaphase? The nucleus disappears and the chromosomes appear in the cytoplasm of the cell

12. What splits up during anaphase? During anaphase, sister chromatids separate, and the centromeres divide. The sister chromatids are pulled apart by the shortening of the spindle fibers 13. During which stage of mitosis are 2 diploid daughter cells formed? During meiosis II, the sister chromatids within the two daughter cells separate, forming four new haploid gametes. 14. During which stage of mitosis does the nucleus reform? sister chromatids line up at the metaphase plate. 15. Fill in the blank: During telophase, the ____ daughter chromosomes __________ uncoil to make chromatin again. 16. What stage of the cell cycle usually happens at the same time as telophase? Cytokinesis usually occurs at the same time as telophase I, forming two haploid daughter cells. 17. What appears to happen during cytokinesis? the cleavage furrow appears suddenly on the surface of the cell and deepens rapidly 18. In what stage of mitosis is this cell pictured below? Metaphae

19. In what stage of mitosis is this cell pictured below? telophase

B. Background on Meiosis In sexually reproducing eukaryotes, cells in the sex organs undergo meiosis to produce sex cells, like egg and sperm. Meiosis results in a reduction of the chromosome number by half from the mother cell to the daughter cells. In meiosis, mother cells are diploid having two sets of chromosomes, while the daughter cells (the egg and sperm) are haploid having only one set of chromosomes. 

Go to the “Snurfle Meiosis and Genetics” activity at: https://biomanbio.com/HTML5GamesandLabs/Genegames/snurflemeiosishtml5page.html

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Click on “Start a New Game!” Click “Press spacebar or Click here to continue,” read the information, then click it again to advance to the main menu.

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Click on “Meiosis interactive!” You will not be able to go back to previous slides for some time – it is recommended that you browse the following questions beforehand. This meiosis activity does not include details about the microtubules and mitotic spindle. Engage with the interactive activity while answering the following questions.

20. What stage of the cell cycle must occur before meiosis starts? Before entering meiosis I, a cell must first go through interphase. 21. What is different about the 2 pieces of chromatin in the animated cell you’re analyzing? interphase and mitosis

22. How many pieces of chromatin does a human cell have? human cell contains a total of 46 chromosomes— 22 pairs common to both males and females, plus two so-called sex chromosomes (X and Y in males, two Xs in females). 23. What does “G” and “g” represent in the cell animation? G is the allele for yellow fur g is the allele for green fur

24. True or false: During interphase, the DNA does not replicate itself. 25. What is the purpose of meiosis? To make gametes (sperm in males or eggs in female) 26. How many divisions occur in meiosis? 2 divisions of meiosis 1 and meiosis 2 27. What are the 4 phases of meiosis II in order?

Prophase Metaphase Anaphase Telophase

28. Fill in the blank: In the cell animation, the chromosomes from the mother and father are called ____autosomal _______ chromosomes because they are the same size and have the same genes (but not always the same alleles for those genes). 29. True or false: The chromatin condenses into chromosomes and the nucleus degrades in prophase I. 30. Define tetrad. a group of four cells produced by the successive divisions of a mother cell a tetrad of spores 31. What happens during crossing over? part of one chromosome is exchanged with another 32. True or false: During telophase, tetrads line up down the middle of the cell. 33. What splits up and moves toward opposite ends of the cell during anaphase I? Anaphase I begins when the two chromosomes of each bivalent (tetrad) separate and start moving toward opposite poles of the cell as a result of the action of the spindle 34. Fill in the blank: ____telophase_______ occurs when the chromosomes reach opposite poles and the nucleus reforms as two independent cells are being formed. 35. True or false: The cytokinesis that occurs during/after telophase I of meiosis happens the same way as cytokinesis occurs during/after telophase of mitosis. 36. Fill in the blanks: At the start of meiosis I, you had 1 ____dploid cell and at the end of meiosis I you have 2 __h_ploid cells because the homologous chromosomes separated. 37. True or false: Homologous chromosomes pair up in tetrads in prophase II. 38. True or false: The chromatin condenses into chromosomes and the nucleus degrades in prophase II. 39. True or false: Chromosomes line up single-file and NOT in pairs in metaphase II. 40. What splits up and moves toward opposite ends of the cell during anaphase II?

sister chromatids separate and migrate to opposite poles True or false: In telophase II, the nucleus reforms, chromosomes uncoil into chromatin, and 4 haploid daughter cells are formed. 41. Name the stage that completely divides the daughter cells and can sometimes happen concurrently with telophase II. anaphase 42. Fill in the blank: When a female organism completes meiosis, the resulting gametes are called ___ oogenesis _____. 

Continue to perform the stages of meiosis again using the male organism. 43. Fill in the blank: When a male organism completes meiosis, the resulting gametes are called ____ gametogenesis. ______. 44. True or false: The 2 cells that result from meiosis I are identical. 45. True or false: The 4 cells that result from meiosis II are identical.

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Once you have completed the activity, you should have been taken back to the main menu for this simulation. Stay on that main menu, as it will be needed for later exercises.

C. Counting chromosomes

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From the main menu titled “Choose your challenge!” click “The Chromosome Quandary!” Click “OK!” to advance. You will not be able to go back to previous slides – it is recommended that you browse the following questions beforehand. Follow the instructions while answering the following questions. 46. What biomolecule makes up chromosomes? Chromosomes are thread-like structures located inside the nucleus of animal and plant cells. Each chromosome is made of protein and a single molecule of deoxyribonucleic acid (DNA). 47. Why is DNA sometimes packaged into chromosomes rather than remaining as uncoiled chromatin? The proteins involved in packaging the DNA, chromosomes are also associated with many proteins required for the processes of gene expression, DNA replication, and DNA repair. 48. Fill in the blank: When you split a chromosome, each sister chromatid is now called a chromosomes 49.How many chromosomes are in the cell pictured below?

4 50. How many chromosomes are in the cell pictured below?

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51. Fill in the blank: Each cell at the end of meiosis has _ __23____ the number of chromosomes as the cell at the start of meiosis. 

Feel free to return to the main menu and take the Meiosis and Genetics Quiz for additional review. 52. Reflect: What are 3 differences you noticed between mitosis and meiosis?

Daughter cells resulting from mitosis are diploid, while those resulting from meiosis are haploid. Daughter cells that are the product of mitosis are genetically identical. Daughter cells produced after meiosis are genetically diverse. Tetrad formation occurs in meiosis but not mitosis

53. What degrades during prophase only to reform in telophase? the nucleus disappears, spindle fibers form, and DNA condenses into chromosomes 54. If a cell with 10 chromosomes divides by mitosis, how many chromosomes will each daughter cell have? 10 chromosomes (each made of two sister chromatids) are present during metaphase. 20 chromosomes are present during anaphase because the sisters chromatids have been pulled apart.

55. If a cell with 40 chromosomes divides by meiosis, how many chromosomes will each daughter cell have? 23

Exercise 2: Time spent in phases of the cell cycle Cells spend a different amount of time in interphase, prophase, metaphase, anaphase, and telophase. You can measure the proportion of time spent in each phase by identifying the stages of several cells from an organism. Growth in an organism is carefully controlled by regulating the cell cycle. In plants, the roots continue to grow as they search for water and nutrients. These regions of growth are good for studying the cell cycle because at any given time, you can find cells that are undergoing mitosis. A. Onion Root Tips In this activity, you will be presented with cells from the tip of an onion root. You will classify each cell based on what phase of the cell cycle it is in (interphase, prophase, metaphase, anaphase, telophase). Remember, cytokinesis usually occurs at the same time as the telophase stage of mitosis, so a cell in telophase will also be undergoing cytokinesis. After classifying the different stages, you will count up the cells found in each phase and use those numbers to predict how much time a dividing cell spends in each phase. You can base your calculation on a total cell cycle of 24 hours. Please note, the images are very small. 

Go to the “Online Onion Root Tips” activity at: http://www.biology.arizona.edu/cell_bio/activities/cell_cycle/cell_cycle.html

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Read the introductory information. Click “next” to advance and “previous” to go back. Follow the instructions while answering the following questions.

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If you are unfamiliar with a term, you can find some definitions by clicking “vocabulary” then “terms to know about mitosis and meiosis,” which opens as a separate window. 56. Describe the distinct role that the spindle fibers (also referred to as microtubules, which they are made of) has in the phases each of the following phases. The role of microtubules during telophase has been provided since it is not described on the website. a. Prophase: is the first phase of mitosis, the process that separates the duplicated genetic material carried in the nucleus of a parent cell into two identical daughter cells. b. Metaphase: the microtubules of the spindle (white) have attached and the chromosomes have lined up on the metaphase plate.

c. Anaphase: the sister chromatids are pulled apart and move toward opposite poles of the cell.

d. Telophase: The spindle fibers (microtubules) disassemble and are no longer visible.

57. Define kinetochore. protein structure associated with duplicated chromatids in eukaryotic cells where the spindle fibers attach during cell division to pull sister chromatids apart.

58. Before classifying all 36 cells, predict the phase in which the cell spends the longest time and why. 24 HOURS

59. In what phase is the cell pictured below?

METAPHASE 60. In what phase is the cell pictured below?

PROPHASE 61. After classifying all 36 cells, count all of the cells in each category and enter your findings under the “number of cells” column in table 1 below. The data for telophase has been provided. Table 1: Determining time spent in phase of the cell cycle Phase

Number of Cells

Interphase Prophase Metaphase Anaphase Telophase Total

36 10 3 2 1 36

% total of cells counted 55.6 28 8.3 5.6 2.8% Should add up to 100%

Time in each phase about 24 hours 30 to 60 minutes 2 to 10 minutes; 2 to 3 minutes 40.32 minutes

62. Estimate the time spent in each phase by using the equation below. Record your percentage under the “% total of cells counted” column for each phase. The data for telophase has been provided. Number of cells in phase / total # of cells in all phases 63. Calculate the amount of time spent in each phase from the percentage of cells in that phase. On average, an onion root cell takes 24 hours (1,440 minutes) to complete

the cell cycle. You can use the equation below and record your data under the column “time in each phase” for each phase. The data for telophase has been provided. % of cells in stage x 1440 minutes = minutes of cell cycle spent in that stage the approximate duration of the cell cycle for the onion cells being studied is 1440 minutes (24 hours) 2 64. In what phase does the cell spend the most time?

interphase 65. Why do you think the cell spends the most time in this phase? Cells spend most of their lives, about 78 percent of the time, not dividing in a phase called interphase.

66. Thinking critically: Can you think of some types of cells that are constantly dividing by mitosis? Mitosis is how somatic—or non-reproductive cells—divide. ... The daughter cells from mitosis are called diploid cells. Diploid cells have two complete sets of chromosomes. Since the daughter cells have exact copies of their parent cell's DNA, no genetic diversity is created through mitosis in normal healthy cells...