L3- Cell Division (Embryology) Flashcards
1
Q
- Which of the following phases is NOT a part of mitosis?
o A) Prophase
o B) Metaphase
o C) Telophase
o D) Interphase
A
- 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.
2
Q
- 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
A
- 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.
3
Q
- 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.
A
- 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.
4
Q
- 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.
A
- 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.
5
Q
- The G1 phase of the cell cycle is when the cell undergoes rapid growth and DNA replication. (True/False)
A
- False
o Rationale: The G1 phase involves growth and preparation for DNA replication, but the actual DNA replication occurs in the S phase.
6
Q
- Meiosis II is similar to mitosis because both involve the separation of sister chromatids. (True/False)
A
- True
o Rationale: Meiosis II is similar to mitosis in that sister chromatids are separated, while meiosis I separates homologous chromosomes.
7
Q
- Cytokinesis is the process that divides the ________ of the cell.
A
- Cytoplasm
o Rationale: Cytokinesis divides the cytoplasm between two daughter cells after the nucleus has divided.
8
Q
- The protein structure on chromatids where the spindle fibers attach during cell division is called the ________.
A
- Kinetochore
o Rationale: The kinetochore is a protein complex at the centromere where spindle fibers attach to move the chromosomes during cell division.
9
Q
Select All That Apply
- 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
A
- 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.
10
Q
Select All That Apply
- 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
A
- 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.
11
Q
- Describe the role of the G2 checkpoint in the cell cycle.
A
- 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.
12
Q
- Explain the difference between mitosis and meiosis in terms of the genetic composition of the daughter cells.
A
- 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.
13
Q
- 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.
A
- 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.
14
Q
- 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.
A
- 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
15
Q
- The process of cell division serves the following purposes EXCEPT:
* A) Growth
* B) Tissue repair
* C) Development of tissues
* D) Protein synthesis
A
- 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.
16
Q
- 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
A
- C) Prophase I
* Rationale: Genetic recombination (crossing over) occurs during prophase I of meiosis, allowing for the exchange of genetic material between homologous chromosomes.
17
Q
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
A
- 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.
18
Q
- Cytokinesis is part of mitosis. (True/False)
A
- False
* Rationale: Cytokinesis is technically not part of mitosis but occurs right after mitosis. It involves the division of the cytoplasm.
19
Q
- The nucleus is divided into two nuclei during the process of mitosis, but no genetic variation occurs in daughter cells. (True/False)
A
- True
* Rationale: Mitosis produces two genetically identical nuclei, and no genetic variation occurs in the daughter cells unless mutations happen during replication.
20
Q
- The ________ phase of mitosis is characterized by the alignment of chromosomes at the equatorial plane.
A
- Metaphase
* Rationale: In metaphase, chromosomes align at the metaphase plate in preparation for segregation.
21
Q
- The complex of proteins involved in the movement of chromosomes during cell division is known as the ________.
A
- Spindle apparatus
* Rationale: The spindle apparatus is responsible for attaching to chromosomes and ensuring their proper distribution during cell division.
22
Q
- DNA replication occurs during the ________ phase of the cell cycle.
A
- S phase
* Rationale: DNA replication occurs during the S (synthesis) phase of interphase.
23
Q
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
A
- 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.
24
Q
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
A
- 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.
25
Q
- What is the significance of checkpoints in the cell cycle, and what happens when they fail?
A
- 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.
26
Q
- Explain the difference between meiosis I and meiosis II in terms of chromosome segregation and number of daughter cells produced.
A
- 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.
27
Q
- 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
A
- 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.
28
Q
- 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.
A
- 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.
29
Q
- 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
A
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.
30
Q
- True or False: If a mutation bypasses the cell cycle checkpoints, this can lead to uncontrolled cell growth and potentially result in cancer.
A
- True
* Rationale: Mutations bypassing cell cycle checkpoints can lead to uncontrolled cell growth, one of the hallmarks of cancer.
31
Q
- 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
A
- A, C
* Rationale: When checkpoints fail, cells can grow uncontrollably, leading to cancer, or accumulate mutations due to unchecked DNA damage.
32
Q
- Describe the function of the M-phase checkpoint in ensuring proper cell division.
A
- The M-phase checkpoint ensures that all chromosomes are properly attached to the spindle apparatus before anaphase begins. This prevents errors in chromosome segregation.
33
Q
- 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.
A
- 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.
34
Q
- Fill in the blank: Cancer results from the ________ growth of cells due to mutations in genes regulating the cell cycle.
A
- Uncontrolled
* Rationale: Cancer involves the uncontrolled growth of cells due to mutations affecting cell cycle regulation.
35
Q
- 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.
A
- 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.
36
Q
- True or False: During meiosis I, the homologous chromosomes undergo crossing over, leading to genetic recombination.
A
- True
* Rationale: Genetic recombination occurs during prophase I, when homologous chromosomes exchange genetic material through crossing over.
37
Q
- 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.
A
- 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.
38
Q
- 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
A
- 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.
39
Q
- 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.
A
- 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.
40
Q
- Fill in the blank: In meiosis, cytokinesis occurs twice, resulting in the formation of ________ genetically unique daughter cells.
A
- Four
* Rationale: Meiosis involves two rounds of cytokinesis, resulting in four genetically unique daughter cells.
41
Q
- 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
A
- 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.
42
Q
- 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
A
- A) RNA and proteins for mitosis
* Rationale: The G2 phase is responsible for the synthesis of RNA and proteins needed for mitosis.
43
Q
- Explain the three key roles of cell division in multicellular organisms: growth, repair, and development of tissues. Provide specific examples for each role.
A
- 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.
44
Q
- 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.
A
- 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.
45
Q
- 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
A
- D) Telophase
* Rationale: Telophase is the phase where chromatids have reached the poles, and the nuclear membrane reforms around the separated chromosomes.
46
Q
- 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
A
- 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.
47
Q
- During metaphase of mitosis, chromosomes align at the center of the cell, also called the metaphase plate. (True/False)
A
- True
* Rationale: In metaphase, chromosomes align at the metaphase plate, which is the central region of the cell.
48
Q
- In prophase I of meiosis, homologous chromosomes pair up and crossing over occurs, resulting in genetic recombination. (True/False)
A
- True
* Rationale: In prophase I of meiosis, homologous chromosomes pair and undergo crossing over, which increases genetic diversity.
49
Q
- During ________ of mitosis, chromosomes become visible as they condense, and the nuclear envelope begins to break down.
A
- Prophase
* Rationale: Prophase is the first stage of mitosis, during which chromosomes condense and the nuclear membrane disintegrates.
50
Q
- In ________, the chromosomes align along the center of the cell, attached to the spindle fibers by their centromeres.
A
- Metaphase
* Rationale: In metaphase, the chromosomes align along the metaphase plate, attached to spindle fibers at their centromeres.
51
Q
- Describe the key events that occur during metaphase of mitosis.
A
- 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.
52
Q
- Explain the difference between prophase in mitosis and prophase I in meiosis.
A
- 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.
53
Q
- 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
A
- 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.
54
Q
- 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.
A
- 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.
55
Q
- 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.
A
- B) Sister chromatids are separated.
* Rationale: In both mitosis and meiosis II, the sister chromatids are separated and pulled to opposite poles.
56
Q
- 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
A
- 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.
57
Q
- 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.
A
- 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.
58
Q
- During meiosis I, homologous chromosomes separate, while during meiosis II, sister chromatids separate. (True/False)
A
- True
* Rationale: During meiosis I, homologous chromosomes are separated, and in meiosis II, sister chromatids are separated, similar to the process in mitosis.
59
Q
- Mitosis and meiosis II are similar because both involve the separation of homologous chromosomes. (True/False)
A
- False
* Rationale: In both mitosis and meiosis II, sister chromatids are separated, not homologous chromosomes. Homologous chromosomes are separated in meiosis I.
60
Q
- During ________, homologous chromosomes pair up and are separated, resulting in the formation of two haploid cells.
A
- Meiosis I
* Rationale: Meiosis I involves the pairing and separation of homologous chromosomes, resulting in haploid cells.
61
Q
- Mitosis produces two genetically identical daughter cells, while meiosis produces ________ genetically distinct daughter cells.
A
- 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.
62
Q
- Explain the major differences between the events of mitosis and meiosis I.
A
- 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.
63
Q
- How are the events of meiosis II similar to those of mitosis, and how are they different?
A
- 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.
64
Q
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
A
- 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.
65
Q
Select all apply
- 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
A
- 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.
66
Q
- 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
A
- (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.
67
Q
- A cell spends the majority of its life cycle in which phase?
o (a) Mitosis
o (b) Interphase
o (c) Cytokinesis
o (d) Meiosis
A
- (b) Interphase Rationale: Cells spend most of their time in interphase, carrying out normal functions and preparing for division.
68
Q
- During which stage of interphase does DNA replication occur?
o (a) G1
o (b) S
o (c) G2
o (d) M
A
- (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.
69
Q
- 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
A
- (a) Mitosis. Rationale: Mitosis is the process of creating two identical daughter cells from a single parent cell.
70
Q
- 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
A
- (b) Meiosis. Rationale: Meiosis is the specialized cell division process that produces gametes (sperm and egg) for sexual reproduction.
71
Q
- How many daughter cells are produced at the end of meiosis?
o (a) 2
o (b) 4
o (c) 6
o (d) 8
A
- (b) 4. Rationale: Meiosis involves two rounds of division (meiosis I and II), resulting in four haploid daughter cells.
72
Q
- 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
A
- (a) Prophase I. Rationale: Homologous chomosomes pair up during Prophase I, a crucial step for genetic recombination.
73
Q
- 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
A
- (a) G1 checkpoint. Rationale: The G1 checkpoint is the primary control point before the cell commits to DNA replication in the S phase.
74
Q
- Daughter cells produced by mitosis are genetically identical. (True/False)
A
- True. Rationale: Mitosis produces identical copies of the parent cell for growth and repair.
75
Q
- Daughter cells produced by meiosis are genetically diverse. (True/False)
A
- True. Rationale: Meiosis generates genetic diversity through crossing over and independent assortment, leading to variations in offspring.
76
Q
- Cytokinesis refers to the division of the cytoplasm. (True/False)
A
- True. Rationale: Cytokinesis is the physical separation of the cytoplasm into two daughter cells after nuclear division.
77
Q
- Chromosomes become visible under a light microscope during Interphase. (True/False)
A
- False. Rationale: Chromosomes condense and become visible during prophase, not interphase. During interphase, chromosomes are in a less compact form called chromatin.
78
Q
- The two types of cell division that occur in eukaryotic cells are __________ and __________.
A
- Mitosis, Meiosis. Rationale: These are the two primary forms of cell division in eukaryotic organisms.
79
Q
- The number of chromosomes in a daughter cell produced by mitosis is ___________ to the number of chromosomes in the parent cell.
A
- Equal. Rationale: Mitosis maintains the chromosome number from parent to daughter cells, ensuring genetic consistency.
80
Q
- The exchange of genetic material between homologous chromosomes during meiosis is called ___________.
A
- Crossing over. Rationale: Crossing over exchanges segments of DNA between homologous chromosomes, contributing to genetic diversity in meiosis.
81
Q
- The failure of cell cycle checkpoints can lead to the development of _________
A
- Cancer. Rationale: When cell cycle checkpoints fail, uncontrolled cell growth and division can occur, a hallmark of cancer.
82
Q
- Describe the four phases of mitosis.
A
- 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.
83
Q
- What are the key differences between mitosis and meiosis?
A
- 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.
84
Q
- 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.
A
- 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.
85
Q
- 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
A
- (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.
86
Q
- Which of the following processes occur during Prophase I of Meiosis? Select all that apply.
* (a) Leptotene
* (b) Cytokinesis
* (c) Zygotene
* (d) Pachytene
A
- (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.
87
Q
- What is the significance of the G1 checkpoint in the cell cycle?
A
- 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.
88
Q
- What are the five sub-stages of Prophase I in Meiosis I, and what key events characterize each sub-stage?
A
- 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
89
Q
- Explain the concept of homologous chromosomes and their significance in meiosis.
A
- 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.
90
Q
- A patient presents with infertility issues. The physician suspects a potential defect in meiosis. Why is meiosis critical for the formation of viable gametes?
A
- 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.
91
Q
- During meiosis, the number of chromosomes is reduced by half in the daughter cells compared to the parent cell. (True/False)
A
- True. Meiosis is a reductional division, meaning it reduces the chromosome number by half, resulting in haploid daughter cells.
92
Q
- Mitosis is a crucial process for wound healing and tissue regeneration. (True/False)
A
- True. Mitosis is essential for repairing damaged tissues and replacing old or damaged cells with new ones.
93
Q
- The phase in which a cell spends most of its life cycle, carrying out its normal functions, is called _______________.
A
- Interphase. This phase includes G1, S, and G2 phases and is when the cell grows and prepares for division.
94
Q
- Meiosis II is often compared to ___________ due to the similarity in the separation of sister chromatids.
A
- 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.
95
Q
- During __________, the cytoplasm divides, ultimately resulting in two separate daughter cells.
A
- Cytokinesis. This process divides the cytoplasm and organelles into two daughter cells at the end of mitosis and meiosis.
