L3- Cell Division (Embryology)

Question 1

1. Which of the following phases is NOT a part of mitosis?
   o A) Prophase
   o B) Metaphase
   o C) Telophase
   o D) Interphase

Answer 1

1. D) Interphase
   o Rationale: Interphase is not part of mitosis; it is the phase where the cell prepares for division by growing and replicating its DNA.

Question 2

2. During which phase of the cell cycle does DNA replication occur?
   o A) G1 phase
   o B) S phase
   o C) G2 phase
   o D) M phase

Answer 2

2. B) S phase
   o Rationale: DNA replication occurs during the S phase of the cell cycle, allowing each chromosome to consist of two sister chromatids.

Question 3

3. Which of the following statements about meiosis is correct?
   o A) It results in two genetically identical daughter cells.
   o B) It results in four genetically identical daughter cells.
   o C) It results in two genetically non-identical daughter cells.
   o D) It results in four genetically non-identical daughter cells.

Answer 3

3. D) It results in four genetically non-identical daughter cells.
   o Rationale: Meiosis produces four daughter cells that are genetically distinct due to recombination and independent assortment.

Question 4

4. What role do spindle fibers play during cell division?
   o A) They help in splitting the nuclear membrane.
   o B) They attach to centromeres and help move chromosomes.
   o C) They replicate the DNA.
   o D) They form the cleavage furrow.

Answer 4

4. B) They attach to centromeres and help move chromosomes.
   o Rationale: Spindle fibers attach to centromeres during metaphase and pull sister chromatids apart during anaphase.

Question 5

5. The G1 phase of the cell cycle is when the cell undergoes rapid growth and DNA replication. (True/False)

Answer 5

5. False
   o Rationale: The G1 phase involves growth and preparation for DNA replication, but the actual DNA replication occurs in the S phase.

Question 6

6. Meiosis II is similar to mitosis because both involve the separation of sister chromatids. (True/False)

Answer 6

6. True
   o Rationale: Meiosis II is similar to mitosis in that sister chromatids are separated, while meiosis I separates homologous chromosomes.

Question 7

7. Cytokinesis is the process that divides the ________ of the cell.

Answer 7

7. Cytoplasm
   o Rationale: Cytokinesis divides the cytoplasm between two daughter cells after the nucleus has divided.

Question 8

8. The protein structure on chromatids where the spindle fibers attach during cell division is called the ________.

Answer 8

8. Kinetochore
   o Rationale: The kinetochore is a protein complex at the centromere where spindle fibers attach to move the chromosomes during cell division.

Question 9

Select All That Apply

9. Which of the following events occur during prophase of mitosis?
   o A) Chromosomes condense and become visible
   o B) Nuclear envelope disappears
   o C) Chromosomes align at the metaphase plate
   o D) Spindle fibers attach to the centromeres

Answer 9

9. A, B, D
   o Rationale: During prophase, chromosomes condense, the nuclear envelope dissolves, and spindle fibers attach to centromeres. Chromosomes do not align at the metaphase plate until metaphase.

Question 10

Select All That Apply

10. Which checkpoints in the cell cycle ensure the proper progression of the cycle?
    o A) G1/S checkpoint
    o B) G2/M checkpoint
    o C) Mitosis checkpoint
    o D) Cytokinesis checkpoint

Answer 10

10. A, B, C
    o Rationale: The G1/S checkpoint ensures the cell is ready for DNA replication, the G2/M checkpoint ensures readiness for mitosis, and the mitosis checkpoint ensures chromosomes are properly aligned before separation.

Question 11

11. Describe the role of the G2 checkpoint in the cell cycle.

Answer 11

11. The G2 checkpoint ensures that all DNA has been replicated correctly and that the cell has all the necessary proteins and organelles for mitosis. If errors are detected, the cell cycle is halted until they are repaired.

Question 12

12. Explain the difference between mitosis and meiosis in terms of the genetic composition of the daughter cells.

Answer 12

12. Mitosis produces two genetically identical daughter cells with the same number of chromosomes as the parent, while meiosis produces four genetically non-identical daughter cells with half the number of chromosomes as the parent.

Question 13

13. A 25-year-old female patient is diagnosed with Turner Syndrome, a condition where one X chromosome is partially or completely missing. Explain the chromosomal abnormality involved and at what point during cell division it could have occurred.

Answer 13

13. Turner syndrome involves a missing or incomplete X chromosome (monosomy X). This abnormality typically arises during meiosis when chromosomes fail to separate properly (nondisjunction), often during anaphase I or II.

Question 14

14. A 30-year-old male presents with a family history of Down syndrome. Explain how trisomy 21 occurs and during which phase of meiosis the error most likely happens.

Answer 14

14. Trisomy 21 (Down syndrome) occurs when there is an extra copy of chromosome 21. This error most commonly occurs during meiosis I, when homologous chromosomes fail to separate properly (nondisjunction), leading to an extra chromosome in the gamete

Question 15

16. The process of cell division serves the following purposes EXCEPT:
    * A) Growth
    * B) Tissue repair
    * C) Development of tissues
    * D) Protein synthesis

Answer 15

16. D) Protein synthesis
    * Rationale: Protein synthesis is not a direct purpose of cell division. The primary functions of cell division include growth, repair, and tissue development.

Question 16

17. In which phase of meiosis does the process of genetic recombination or “crossing over” occur?
    * A) Metaphase I
    * B) Anaphase I
    * C) Prophase I
    * D) Telophase I

Answer 16

17. C) Prophase I
    * Rationale: Genetic recombination (crossing over) occurs during prophase I of meiosis, allowing for the exchange of genetic material between homologous chromosomes.

Question 17

18.
Which of the following checkpoints is crucial for determining whether the cell can proceed to DNA replication?
* A) G2/M checkpoint
* B) M checkpoint
* C) G1/S checkpoint
* D) Cytokinesis checkpoint

Answer 17

18. C) G1/S checkpoint
    * Rationale: The G1/S checkpoint ensures the cell is ready for DNA replication, checking for cell size, nutrients, and DNA integrity before the S phase.

Question 18

19. Cytokinesis is part of mitosis. (True/False)

Answer 18

19. False
    * Rationale: Cytokinesis is technically not part of mitosis but occurs right after mitosis. It involves the division of the cytoplasm.

Question 19

20. The nucleus is divided into two nuclei during the process of mitosis, but no genetic variation occurs in daughter cells. (True/False)

Answer 19

20. True
    * Rationale: Mitosis produces two genetically identical nuclei, and no genetic variation occurs in the daughter cells unless mutations happen during replication.

Question 20

21. The ________ phase of mitosis is characterized by the alignment of chromosomes at the equatorial plane.

Answer 20

21. Metaphase
    * Rationale: In metaphase, chromosomes align at the metaphase plate in preparation for segregation.

Question 21

22. The complex of proteins involved in the movement of chromosomes during cell division is known as the ________.

Answer 21

22. Spindle apparatus
    * Rationale: The spindle apparatus is responsible for attaching to chromosomes and ensuring their proper distribution during cell division.

Question 22

23. DNA replication occurs during the ________ phase of the cell cycle.

Answer 22

23. S phase
    * Rationale: DNA replication occurs during the S (synthesis) phase of interphase.

Question 23

Select all that apply - 24. Which of the following occurs during the G1 phase of interphase?
o A) Rapid cell growth
o B) DNA replication
o C) Preparation for mitosis
o D) Production of RNA and proteins necessary for cell division

Answer 23

24. A, D
    o Rationale: During the G1 phase, the cell grows rapidly and produces RNA and proteins essential for DNA replication and division. DNA replication occurs during the S phase.

Question 24

Select all that apply - 25. Which of the following events are involved in telophase of mitosis?
o A) Chromosomes begin to decondense
o B) Cleavage furrow forms
o C) Spindle fibers dissolve
o D) Chromatids are pulled to opposite poles of the cell

Answer 24

25. A, B, C
    o Rationale: In telophase, chromosomes begin to decondense, a cleavage furrow forms, and the spindle fibers disintegrate. The pulling of chromatids to opposite poles happens during anaphase.

Question 25

26. What is the significance of checkpoints in the cell cycle, and what happens when they fail?

Answer 25

26. Checkpoints ensure the proper progression of the cell cycle. The G1 checkpoint checks for cell size and DNA damage, the G2 checkpoint ensures all DNA is correctly replicated, and the M checkpoint verifies the proper alignment of chromosomes before separation. If checkpoints fail, it can lead to uncontrolled cell growth, mutations, or cancer.

Question 26

27. Explain the difference between meiosis I and meiosis II in terms of chromosome segregation and number of daughter cells produced.

Answer 26

27. In meiosis I, homologous chromosomes are separated, resulting in two cells with half the number of chromosomes (haploid). In meiosis II, sister chromatids are separated, producing four genetically non-identical haploid cells.

Question 27

30. A 40-year-old woman undergoing fertility treatment is concerned about the increased risk of chromosomal abnormalities such as trisomy 21. Explain how the age-related risk of nondisjunction in meiosis might lead to conditions like Down syndrome

Answer 27

30. As a woman ages, the risk of nondisjunction during meiosis increases, especially in oocytes. This results in errors in chromosome separation, leading to conditions like trisomy 21 (Down syndrome). Nondisjunction is most likely to occur during meiosis I.

Question 28

31. A newborn is diagnosed with Klinefelter syndrome (XXY). Describe how this chromosomal abnormality arises and explain the stage of cell division where this error could have occurred.

Answer 28

31. Klinefelter syndrome occurs when an individual has an extra X chromosome (XXY). This chromosomal abnormality arises from nondisjunction during meiosis I or II, where sex chromosomes fail to separate properly, resulting in an extra chromosome.

Question 29

32. Which of the following checkpoints ensures that the cell's DNA is correctly replicated before it proceeds to mitosis? * A) G1/S checkpoint * B) G2/M checkpoint * C) M checkpoint * D) Cytokinesis checkpoint

Answer 29

G2/M checkpoint * Rationale: The G2/M checkpoint ensures that all DNA is correctly replicated and that the cell has the components necessary to proceed to mitosis.

Question 30

33. True or False: If a mutation bypasses the cell cycle checkpoints, this can lead to uncontrolled cell growth and potentially result in cancer.

Answer 30

33. True * Rationale: Mutations bypassing cell cycle checkpoints can lead to uncontrolled cell growth, one of the hallmarks of cancer.

Question 31

34. Which of the following are possible outcomes when cell cycle checkpoints fail? * A) Uncontrolled cell growth * B) Cells remain in G1 phase permanently * C) Mutations accumulate * D) Cells undergo apoptosis

Answer 31

34. A, C * Rationale: When checkpoints fail, cells can grow uncontrollably, leading to cancer, or accumulate mutations due to unchecked DNA damage.

Question 32

35. Describe the function of the M-phase checkpoint in ensuring proper cell division.

Answer 32

35. The M-phase checkpoint ensures that all chromosomes are properly attached to the spindle apparatus before anaphase begins. This prevents errors in chromosome segregation.

Question 33

36. Which of the following accurately describes cancer in relation to the cell cycle? * A) Cancer cells undergo normal cell cycle regulation. * B) Cancer cells are highly specialized and do not divide. * C) Cancer cells ignore cell cycle checkpoints, leading to rapid proliferation. * D) Cancer cells halt in the G1 phase and cannot divide.

Answer 33

36. C) Cancer cells ignore cell cycle checkpoints, leading to rapid proliferation. * Rationale: Cancer cells often result from the failure to respond to normal cell cycle regulation, causing unchecked division.

Question 34

37. Fill in the blank: Cancer results from the ________ growth of cells due to mutations in genes regulating the cell cycle.

Answer 34

37. Uncontrolled * Rationale: Cancer involves the uncontrolled growth of cells due to mutations affecting cell cycle regulation.

Question 35

38. Which of the following is a major difference between meiosis I and meiosis II? * A) Meiosis I separates sister chromatids, while meiosis II separates homologous chromosomes. * B) Meiosis I results in haploid cells, while meiosis II results in diploid cells. * C) Meiosis I separates homologous chromosomes, while meiosis II separates sister chromatids. * D) Meiosis I results in diploid cells, while meiosis II results in haploid cells.

Answer 35

38. C) Meiosis I separates homologous chromosomes, while meiosis II separates sister chromatids. * Rationale: The key distinction is that meiosis I separates homologous chromosomes, and meiosis II separates sister chromatids.

Question 36

39. True or False: During meiosis I, the homologous chromosomes undergo crossing over, leading to genetic recombination.

Answer 36

39. True * Rationale: Genetic recombination occurs during prophase I, when homologous chromosomes exchange genetic material through crossing over.

Question 37

40. Which of the following occurs during the zygotene stage of prophase I in meiosis? * A) Chromosomes condense and become visible. * B) Homologous chromosomes pair up and form bivalents. * C) Chromosomes separate except where crossing over occurs. * D) Spindle fibers attach to centromeres.

Answer 37

40. B) Homologous chromosomes pair up and form bivalents. * Rationale: During zygotene, homologous chromosomes pair and form bivalents, which are critical for crossing over later in prophase I.

Question 38

41. Match the following stages of prophase I with their correct descriptions: * A) Leptotene 1)Chromosomes appear as individual threads * B) Pachytene o 2) Crossing over occurs between homologous chromosomes * C) Diplotene o 3) Chromosomes begin to separate except where crossing over occurred

Answer 38

41. A-1, B-2, C-3 * Rationale: Leptotene is the stage where chromosomes appear as threads, pachytene is where crossing over occurs, and diplotene is when chromosomes begin to separate except at crossover points.

Question 39

42. Which of the following best describes cytokinesis in mitosis? * A) The cytoplasm divides equally between four daughter cells. * B) The cytoplasm divides equally between two identical daughter cells. * C) The cytoplasm divides unequally between two identical daughter cells. * D) The cytoplasm divides equally between four genetically unique daughter cells.

Answer 39

42. B) The cytoplasm divides equally between two identical daughter cells. * Rationale: Cytokinesis in mitosis produces two genetically identical daughter cells with equal division of cytoplasm.

Question 40

43. Fill in the blank: In meiosis, cytokinesis occurs twice, resulting in the formation of ________ genetically unique daughter cells.

Answer 40

43. Four * Rationale: Meiosis involves two rounds of cytokinesis, resulting in four genetically unique daughter cells.

Question 41

44. During which phase of the cell cycle does the cell grow in size and synthesize proteins necessary for DNA replication? * A) G1 phase * B) S phase * C) G2 phase * D) M phase

Answer 41

44. A) G1 phase * Rationale: The G1 phase is the growth phase in which the cell increases in size and synthesizes proteins necessary for DNA replication.

Question 42

45. Which of the following is produced during the G2 phase of the cell cycle? * A) RNA and proteins for mitosis * B) DNA * C) Spindle fibers * D) Cleavage furrow

Answer 42

45. A) RNA and proteins for mitosis * Rationale: The G2 phase is responsible for the synthesis of RNA and proteins needed for mitosis.

Question 43

46. Explain the three key roles of cell division in multicellular organisms: growth, repair, and development of tissues. Provide specific examples for each role.

Answer 43

46. Cell division plays the following three key roles in multicellular organisms: Growth: Cell division increases the number of cells, allowing the organism to grow in size and complexity. For example, during childhood, cell division helps the body grow taller and stronger. Repair: It replaces damaged or dead cells, allowing tissues to heal and recover from injuries. For instance, when someone gets a cut or breaks a bone, cell division replaces damaged cells and helps the wound or fracture heal. Development of Tissues: Cell division and differentiation create specialized cells that form tissues and organs, ensuring proper body structure and function. For example, during embryonic development, cell division forms different types of tissues such as muscle, nerve, and epithelial tissues.

Question 44

47. Which of the following best describes what occurs during anaphase of mitosis? * A) Chromosomes align at the equatorial plate. * B) Sister chromatids separate and move to opposite poles. * C) Nuclear membrane reforms around the chromosomes. * D) Chromosomes condense and spindle fibers form.

Answer 44

47. B) Sister chromatids separate and move to opposite poles. * Rationale: During anaphase, the sister chromatids are pulled apart by the spindle fibers toward opposite poles of the cell.

Question 45

48. Which phase of mitosis is characterized by the complete separation of the chromatids and the reformation of the nuclear envelope? * A) Prophase * B) Metaphase * C) Anaphase * D) Telophase

Answer 45

48. D) Telophase * Rationale: Telophase is the phase where chromatids have reached the poles, and the nuclear membrane reforms around the separated chromosomes.

Question 46

49. During which stage of the cell cycle does the cell prepare for mitosis by producing proteins necessary for spindle formation and other mitotic machinery? * A) G1 phase * B) S phase * C) G2 phase * D) M phase

Answer 46

49. C) G2 phase * Rationale: During the G2 phase, the cell produces proteins and other components necessary for mitosis, ensuring that all organelles are ready for cell division.

Question 47

50. During metaphase of mitosis, chromosomes align at the center of the cell, also called the metaphase plate. (True/False)

Answer 47

50. True * Rationale: In metaphase, chromosomes align at the metaphase plate, which is the central region of the cell.

Question 48

51. In prophase I of meiosis, homologous chromosomes pair up and crossing over occurs, resulting in genetic recombination. (True/False)

Answer 48

51. True * Rationale: In prophase I of meiosis, homologous chromosomes pair and undergo crossing over, which increases genetic diversity.

Question 49

52. During ________ of mitosis, chromosomes become visible as they condense, and the nuclear envelope begins to break down.

Answer 49

52. Prophase * Rationale: Prophase is the first stage of mitosis, during which chromosomes condense and the nuclear membrane disintegrates.

Question 50

53. In ________, the chromosomes align along the center of the cell, attached to the spindle fibers by their centromeres.

Answer 50

53. Metaphase * Rationale: In metaphase, the chromosomes align along the metaphase plate, attached to spindle fibers at their centromeres.

Question 51

54. Describe the key events that occur during metaphase of mitosis.

Answer 51

54. In metaphase, the chromosomes align at the metaphase plate, an imaginary line in the middle of the cell. Each chromosome is attached to spindle fibers from opposite poles by their centromeres, ensuring that when they are pulled apart during anaphase, each daughter cell will receive one chromatid from each chromosome.

Question 52

55. Explain the difference between prophase in mitosis and prophase I in meiosis.

Answer 52

55. In prophase of mitosis, the nuclear envelope breaks down, chromosomes condense, and spindle fibers form. In prophase I of meiosis, homologous chromosomes pair up and undergo crossing over, a process unique to meiosis that allows for genetic recombination between maternal and paternal chromosomes.

Question 53

56. Which of the following events occur during prophase of mitosis? * A) Chromosomes condense and become visible * B) Nuclear envelope breaks down * C) Homologous chromosomes undergo crossing over * D) Spindle fibers begin to form

Answer 53

56. A, B, D * Rationale: During prophase of mitosis, chromosomes condense, the nuclear envelope breaks down, and spindle fibers begin to form. Crossing over is unique to meiosis, not mitosis.

Question 54

57. Which of the following is a key difference between mitosis and meiosis I? * A) Mitosis produces haploid cells, while meiosis I produces diploid cells. * B) Mitosis separates homologous chromosomes, while meiosis I separates sister chromatids. * C) Mitosis results in two identical daughter cells, while meiosis I results in two genetically unique cells. * D) Mitosis involves crossing over, while meiosis I does not.

Answer 54

57. C) Mitosis results in two identical daughter cells, while meiosis I results in two genetically unique cells. * Rationale: Mitosis produces two identical diploid cells, while meiosis I reduces the chromosome number by half and produces two genetically distinct haploid cells due to crossing over and independent assortment.

Question 55

58. Which of the following occurs during both mitosis and meiosis II? * A) Homologous chromosomes are separated. * B) Sister chromatids are separated. * C) Crossing over between chromosomes occurs. * D) The cell divides twice to produce four daughter cells.

Answer 55

58. B) Sister chromatids are separated. * Rationale: In both mitosis and meiosis II, the sister chromatids are separated and pulled to opposite poles.

Question 56

59. How many daughter cells are produced at the end of mitosis, meiosis I, and meiosis II respectively? * A) Two, two, and four * B) Two, two, and two * C) Four, two, and two * D) Two, four, and four

Answer 56

59. A) Two, two, and four * Rationale: Mitosis results in two daughter cells, meiosis I results in two cells, and meiosis II completes the division to form four total daughter cells.

Question 57

60. Which of the following occurs in both mitosis and meiosis but happens only during meiosis I? * A) Chromosomes align at the metaphase plate. * B) Sister chromatids are separated. * C) Homologous chromosomes pair and undergo crossing over. * D) The nuclear envelope reforms.

Answer 57

60. C) Homologous chromosomes pair and undergo crossing over. * Rationale: Crossing over and homologous chromosome pairing are unique to meiosis I and do not occur in mitosis.

Question 58

61. During meiosis I, homologous chromosomes separate, while during meiosis II, sister chromatids separate. (True/False)

Answer 58

61. True * Rationale: During meiosis I, homologous chromosomes are separated, and in meiosis II, sister chromatids are separated, similar to the process in mitosis.

Question 59

62. Mitosis and meiosis II are similar because both involve the separation of homologous chromosomes. (True/False)

Answer 59

62. False * Rationale: In both mitosis and meiosis II, sister chromatids are separated, not homologous chromosomes. Homologous chromosomes are separated in meiosis I.

Question 60

63. During ________, homologous chromosomes pair up and are separated, resulting in the formation of two haploid cells.

Answer 60

63. Meiosis I * Rationale: Meiosis I involves the pairing and separation of homologous chromosomes, resulting in haploid cells.

Question 61

64. Mitosis produces two genetically identical daughter cells, while meiosis produces ________ genetically distinct daughter cells.

Answer 61

64. Four * Rationale: Meiosis results in four genetically distinct daughter cells due to the two rounds of division and the process of recombination and independent assortment.

Question 62

65. Explain the major differences between the events of mitosis and meiosis I.

Answer 62

65. Mitosis produces two genetically identical diploid cells, with no crossing over, and involves the separation of sister chromatids. Meiosis I, on the other hand, results in the separation of homologous chromosomes, reduces the chromosome number by half, and includes crossing over to create genetic diversity.

Question 63

66. How are the events of meiosis II similar to those of mitosis, and how are they different?

Answer 63

66. Meiosis II and mitosis are similar because both involve the separation of sister chromatids. However, meiosis II follows meiosis I, so the resulting daughter cells are haploid, while mitosis results in diploid daughter cells.

Question 64

Select All That Apply 67. Which of the following events occur in meiosis I but not in mitosis? * A) Homologous chromosomes undergo crossing over * B) Chromosomes align at the metaphase plate * C) Chromosomes condense and become visible * D) Homologous chromosomes are separated

Answer 64

67. A, D * Rationale: Crossing over and the separation of homologous chromosomes are unique to meiosis I. Chromosome alignment and condensation occur in both mitosis and meiosis.

Question 65

Select all apply 68. Which of the following events occur in both meiosis II and mitosis? * A) Separation of sister chromatids * B) Formation of spindle fibers * C) Crossing over of homologous chromosomes * D) Cytokinesis

Answer 65

68. A, B, D * Rationale: Separation of sister chromatids, spindle fiber formation, and cytokinesis occur in both mitosis and meiosis II. Crossing over only occurs in meiosis I.

Question 66

69. Which of the following is NOT a function of cell division? o (a) Tissue repair o (b) Organismal reproduction o (c) Energy production o (d) Replacement of dead cells

Answer 66

69. (c) Energy production. Rationale: The primary functions of cell division are growth, repair, and reproduction, not energy production. Cellular respiration is responsible for energy production.

Question 67

70. A cell spends the majority of its life cycle in which phase? o (a) Mitosis o (b) Interphase o (c) Cytokinesis o (d) Meiosis

Answer 67

70. (b) Interphase Rationale: Cells spend most of their time in interphase, carrying out normal functions and preparing for division.

Question 68

71. During which stage of interphase does DNA replication occur? o (a) G1 o (b) S o (c) G2 o (d) M

Answer 68

71. (b) S. Rationale: The S phase, or synthesis phase, is when DNA replication takes place, ensuring each daughter cell receives a complete copy of the genome.

Question 69

72. The process by which a single parent cell divides to make two new daughter cells is called: o (a) Mitosis o (b) Meiosis o (c) Binary fission o (d) Replication

Answer 69

72. (a) Mitosis. Rationale: Mitosis is the process of creating two identical daughter cells from a single parent cell.

Question 70

73. The special type of cell division that occurs in the testes and ovaries to produce sperm and ova is called: o (a) Mitosis o (b) Meiosis o (c) Binary fission o (d) Replication

Answer 70

73. (b) Meiosis. Rationale: Meiosis is the specialized cell division process that produces gametes (sperm and egg) for sexual reproduction.

Question 71

74. How many daughter cells are produced at the end of meiosis? o (a) 2 o (b) 4 o (c) 6 o (d) 8

Answer 71

74. (b) 4. Rationale: Meiosis involves two rounds of division (meiosis I and II), resulting in four haploid daughter cells.

Question 72

75. During which phase of meiosis do homologous chromosomes pair up? o (a) Prophase I o (b) Metaphase I o (c) Anaphase I o (d) Telophase I

Answer 72

75. (a) Prophase I. Rationale: Homologous chomosomes pair up during Prophase I, a crucial step for genetic recombination.

Question 73

76. Which of the following checkpoints ensures the cell is ready to proceed from G1 to S phase? o (a) G1 checkpoint o (b) G2 checkpoint o (c) Mitosis checkpoint o (d) None of the above

Answer 73

76. (a) G1 checkpoint. Rationale: The G1 checkpoint is the primary control point before the cell commits to DNA replication in the S phase.

Question 74

77. Daughter cells produced by mitosis are genetically identical. (True/False)

Answer 74

77. True. Rationale: Mitosis produces identical copies of the parent cell for growth and repair.

Question 75

78. Daughter cells produced by meiosis are genetically diverse. (True/False)

Answer 75

78. True. Rationale: Meiosis generates genetic diversity through crossing over and independent assortment, leading to variations in offspring.

Question 76

79. Cytokinesis refers to the division of the cytoplasm. (True/False)

Answer 76

79. True. Rationale: Cytokinesis is the physical separation of the cytoplasm into two daughter cells after nuclear division.

Question 77

80. Chromosomes become visible under a light microscope during Interphase. (True/False)

Answer 77

80. False. Rationale: Chromosomes condense and become visible during prophase, not interphase. During interphase, chromosomes are in a less compact form called chromatin.

Question 78

81. The two types of cell division that occur in eukaryotic cells are __________ and __________.

Answer 78

81. Mitosis, Meiosis. Rationale: These are the two primary forms of cell division in eukaryotic organisms.

Question 79

82. The number of chromosomes in a daughter cell produced by mitosis is ___________ to the number of chromosomes in the parent cell.

Answer 79

82. Equal. Rationale: Mitosis maintains the chromosome number from parent to daughter cells, ensuring genetic consistency.

Question 80

83. The exchange of genetic material between homologous chromosomes during meiosis is called ___________.

Answer 80

83. Crossing over. Rationale: Crossing over exchanges segments of DNA between homologous chromosomes, contributing to genetic diversity in meiosis.

Question 81

84. The failure of cell cycle checkpoints can lead to the development of _________

Answer 81

84. Cancer. Rationale: When cell cycle checkpoints fail, uncontrolled cell growth and division can occur, a hallmark of cancer.

Question 82

85. Describe the four phases of mitosis.

Answer 82

85. Prophase: Chromosomes condense, the nuclear envelope breaks down, and the spindle apparatus forms. Metaphase: Chromosomes line up along the cell equator, attached to spindle fibers. Anaphase: Sister chromatids separate and move to opposite poles of the cell. Telophase: Chromosomes decondense, nuclear envelopes reform, and cytokinesis begins.

Question 83

86. What are the key differences between mitosis and meiosis?

Answer 83

86. Mitosis produces two genetically identical daughter cells with the same chromosome number as the parent cell. It is used for growth, repair, and asexual reproduction. Meiosis produces four genetically diverse daughter cells, each with half the number of chromosomes as the parent cell. It is involved in sexual reproduction and produces gametes.

Question 84

87. A 25-year-old pregnant woman undergoes prenatal testing. The results reveal that her fetus has trisomy 21 (Down Syndrome). Briefly explain what trisomy 21 is and how this chromosomal abnormality could have occurred during cell division.

Answer 84

87. Trisomy 21 (Down Syndrome) occurs when an individual has an extra copy of chromosome 21, resulting in a total of three copies instead of the usual two. This error typically occurs during meiosis, when chromosomes fail to separate properly (nondisjunction). As a result, one gamete (sperm or egg) may end up with an extra copy of chromosome 21. When this gamete fuses with a normal gamete during fertilization, the resulting zygote will have three copies of chromosome 21.

Question 85

88. Which of the following statements regarding interphase are TRUE? Select all that apply. o (a) It is the resting phase between cell divisions o (b) DNA replication occurs during interphase o (c) It is the shortest phase of the cell cycle o (d) The cell grows in size during interphase

Answer 85

88. (a) It is the resting phase between cell divisions, (b) DNA replication occurs during interphase, and (d) The cell grows in size during interphase. Rationale: Interphase is an active phase where the cell prepares for division. DNA replicates, organelles duplicate, and the cell grows. It is not the shortest phase.

Question 86

89. Which of the following processes occur during Prophase I of Meiosis? Select all that apply. * (a) Leptotene * (b) Cytokinesis * (c) Zygotene * (d) Pachytene

Answer 86

89. (a) Leptotene, (c) Zygotene, and (d) Pachytene. Rationale: These are all substages within Prophase I of Meiosis I, characterized by specific events like chromosome condensation and pairing. Cytokinesis occurs after nuclear division.

Question 87

90. What is the significance of the G1 checkpoint in the cell cycle?

Answer 87

90. The G1 checkpoint is a critical regulatory point in the cell cycle that determines if a cell should commit to DNA replication and proceed to the S phase. It ensures the cell is large enough, has adequate resources, and has no DNA damage before it initiates the process of replication.

Question 88

91. What are the five sub-stages of Prophase I in Meiosis I, and what key events characterize each sub-stage?

Answer 88

91. The five substages of Prophase I are: Leptotene: * Chromosomes appear as individual threads * Attached at one end to the nuclear envelope * Chromosomes show beads (chromomeres) throughout their length * Zygotene: * Homologous chromosomes come together * Homologous chromosomes pair point to point and called bivalents * These are held together by a fibrillar band called synaptonemal complex Pachytene: * Shortening and thickening of chromosomes continue * Two chromatids of a chromosome become visible * Four chromatids of 2 chromosomes are called tetrad * Chromatids from 2 chromosomes coil around each other * Exchange of DNA occurs by breaking and rejoining of chromatids – crossing Diplotene: * Chromosomes become short and thick * Begin to separate except where the crossing over has occurred * As the chromosomes become short, the crossing points become visible * Diakinesis: * Chromosomes become short, thick and get separated, but homologous chromosomes lie together

Question 89

92. Explain the concept of homologous chromosomes and their significance in meiosis.

Answer 89

92. Homologous chromosomes are pairs of chromosomes that carry the same genes at the same loci, one chromosome from each parent. In meiosis, the pairing and separation of homologous chromosomes are essential for reducing the chromosome number by half and ensuring that each gamete receives a complete set of chromosomes.

Question 90

93. A patient presents with infertility issues. The physician suspects a potential defect in meiosis. Why is meiosis critical for the formation of viable gametes?

Answer 90

93. Meiosis is crucial for fertility because it produces haploid gametes (sperm and egg cells). During fertilization, these haploid gametes fuse to form a diploid zygote with the correct number of chromosomes. Defects in meiosis can lead to gametes with an incorrect number of chromosomes (aneuploidy), often resulting in infertility or birth defects.

Question 91

94. During meiosis, the number of chromosomes is reduced by half in the daughter cells compared to the parent cell. (True/False)

Answer 91

94. True. Meiosis is a reductional division, meaning it reduces the chromosome number by half, resulting in haploid daughter cells.

Question 92

95. Mitosis is a crucial process for wound healing and tissue regeneration. (True/False)

Answer 92

95. True. Mitosis is essential for repairing damaged tissues and replacing old or damaged cells with new ones.

Question 93

96. The phase in which a cell spends most of its life cycle, carrying out its normal functions, is called _______________.

Answer 93

96. Interphase. This phase includes G1, S, and G2 phases and is when the cell grows and prepares for division.

Question 94

97. Meiosis II is often compared to ___________ due to the similarity in the separation of sister chromatids.

Answer 94

97. Mitosis. Meiosis II and mitosis are similar in that they both involve the separation of sister chromatids, but meiosis II starts with a haploid cell while mitosis starts with a diploid cell.

Question 95

98. During __________, the cytoplasm divides, ultimately resulting in two separate daughter cells.

Answer 95

98. Cytokinesis. This process divides the cytoplasm and organelles into two daughter cells at the end of mitosis and meiosis.