D2.1-2.1.8
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Questions and Answers

What occurs before DNA replication in the cell cycle?

  • The cell prepares for nuclear division. (correct)
  • Cohesin begins to break down.
  • The DNA condenses into chromosomes.
  • Single chromatids are produced.
  • What structure holds the identical DNA molecules together after replication?

  • Cohesin loops (correct)
  • Nuclear envelope
  • Telomeres
  • Centromeres
  • During which phase are the cohesin loops cut?

  • Anaphase (correct)
  • Telophase
  • Metaphase
  • Prophase
  • What is the condition of DNA before it is replicated?

    <p>It exists as long single molecules.</p> Signup and view all the answers

    What is a false hypothesis regarding the behavior of chromatids during division?

    <p>A single centromere holds the chromatids together.</p> Signup and view all the answers

    What is the process called by which a mother cell produces new cells?

    <p>Cell division</p> Signup and view all the answers

    Which statement accurately reflects the theory of cell generation?

    <p>New cells are produced from pre-existing cells.</p> Signup and view all the answers

    What happens to the mother cell during cell division?

    <p>It disappears as an entity.</p> Signup and view all the answers

    From what did all cells in a person's body originate?

    <p>The division of a zygote.</p> Signup and view all the answers

    Which component is NOT a direct ancestor of the cells in our bodies today?

    <p>Cells in unrelated species</p> Signup and view all the answers

    What does the continuity of life imply about human cells?

    <p>They can be traced back to the earliest cells on Earth.</p> Signup and view all the answers

    Which statement best describes the significance of cell division in living organisms?

    <p>It is crucial for maintenance, growth, and reproduction.</p> Signup and view all the answers

    Which organization is attempting to create new living cells from lifeless components?

    <p>BaSyC</p> Signup and view all the answers

    What occurs at the end of prophase regarding the nuclear membrane?

    <p>It breaks down.</p> Signup and view all the answers

    Which structure grows microtubules towards the end of prophase?

    <p>Microtubule organizing centres (MTOCs)</p> Signup and view all the answers

    During metaphase, what is the role of spindle microtubules?

    <p>They align chromosomes on the equator.</p> Signup and view all the answers

    What is tested during metaphase to ensure proper attachment?

    <p>The tension of the spindle microtubules</p> Signup and view all the answers

    What type of structure do the microtubules form during prophase?

    <p>Spindle-shaped array</p> Signup and view all the answers

    What happens to sister chromatids during metaphase?

    <p>They stay attached to each other.</p> Signup and view all the answers

    Which of the following structures directly interact with the chromosomes during metaphase?

    <p>Kinetochore spindle microtubules</p> Signup and view all the answers

    What is the primary function of microtubules during the metaphase stage of mitosis?

    <p>To facilitate chromosome alignment</p> Signup and view all the answers

    What prevents chromosomes from being pulled to either pole during the late stages of metaphase?

    <p>Cohesin loops</p> Signup and view all the answers

    At what stage are chromosomes aligned at the equator of the cell?

    <p>Metaphase</p> Signup and view all the answers

    Which structure is responsible for pulling chromosomes to the poles during anaphase?

    <p>Spindle microtubules</p> Signup and view all the answers

    What happens to the cohesin loops during anaphase?

    <p>They are cut</p> Signup and view all the answers

    What initiates the movement of chromosomes towards the poles in anaphase?

    <p>Kinetochore shortening</p> Signup and view all the answers

    By the end of which phase are chromosomes no longer held together by cohesin?

    <p>Anaphase</p> Signup and view all the answers

    What stabilizes the chromosomes at the equator during metaphase?

    <p>Cohesin connections</p> Signup and view all the answers

    What defines the formation of genetically identical chromosomes in anaphase?

    <p>Separation of sister chromatids</p> Signup and view all the answers

    What happens to chromosomes during interphase?

    <p>They are dispersed and decondensed.</p> Signup and view all the answers

    What is a key event that occurs during telophase?

    <p>Chromosomes are dispersed into the nucleus.</p> Signup and view all the answers

    What primarily occurs in the cytoplasm during interphase?

    <p>The cell grows and metabolically prepares for mitosis.</p> Signup and view all the answers

    What occurs immediately after cytokinesis?

    <p>The cell starts interphase, doubling in size.</p> Signup and view all the answers

    What is the state of genes in decondensed chromosomes?

    <p>They are transcribed and translated into proteins.</p> Signup and view all the answers

    What occurs at the end of anaphase?

    <p>Chromosomes reach the poles.</p> Signup and view all the answers

    What happens to the chromosomes during telophase?

    <p>They spread out to form dispersed chromatin.</p> Signup and view all the answers

    What initiates cytokinesis during the mitotic process?

    <p>The appearance of a cleavage furrow.</p> Signup and view all the answers

    What typically happens to daughter cells after completing mitosis?

    <p>They enter interphase.</p> Signup and view all the answers

    Where does the nuclear membrane reform during telophase?

    <p>Near the chromosomes at each pole.</p> Signup and view all the answers

    During which phase are chromosomes tightly grouped near the MTOC?

    <p>Telophase.</p> Signup and view all the answers

    What is the primary characteristic of chromosomes at the conclusion of anaphase?

    <p>They have reached the poles but have not decondensed.</p> Signup and view all the answers

    Which of the following statements is true concerning the events of cytogenesis?

    <p>A furrow forms at the equator during cytokinesis.</p> Signup and view all the answers

    Study Notes

    Cell Division in Living Organisms

    • All organisms need new cells for growth, maintenance, and reproduction.
    • This is achieved through cell division.
    • A mother cell divides into two daughter cells.
    • The mother cell is no longer a separate entity.
    • New cells are always created from pre-existing cells (strong evidence for this theory).
    • Our bodies are made of trillions of cells, each originating from the initial zygote.
    • The zygote is formed from the fusion of sperm and egg.
    • The origins of our cells can be traced back to earlier generations.
    • This demonstrates continuity of life from the earliest cells to the cells in our bodies today.

    Cytokinesis in Animal Cells

    • Cytokinesis divides the cytoplasm during cell division.
    • It happens after nuclear division (mitosis in mother cells).
    • Cytoplasm and contents are divided between two daughter cells.
    • Animal cells form a cleavage furrow around the center.
    • Contractile proteins (actin and myosin) pull the plasma membrane inwards, pinching it apart.

    Cytokinesis in Plant Cells

    • Plant cells use a different approach.
    • Microtubules form a scaffold at the equator.
    • Vesicles fuse to create a cell plate.
    • This develops into a new cell wall, separating the two cells.
    • The cell plate connects to existing plasma membranes to complete cell division.

    Equal and Unequal Cytokinesis

    • Equal cytokinesis divides cytoplasm evenly. Happens in growing root tips.
    • Unequal cytokinesis divides cytoplasm unequally.
    • Resulting smaller cells can still function if they receive enough organelles.
    • Mitochondria, for instance, require pre-existing ones to be viable.

    Budding in Yeast

    • Yeast reproduces asexually.
    • A small outgrowth (bud) forms on the mother cell.
    • Nuclei divide.
    • Bud receives a portion of cytoplasm.
    • Bud eventually separates from the mother cell, leaving a scar.

    Oogenesis in Humans

    • One large oocyte and small polar bodies are produced in each meiotic cycle.
    • The large oocyte receives most of the cytoplasm, providing resources for the developing embryo.
    • The polar bodies eventually degenerate and are not involved in fertilization.

    Mitosis and Meiosis in Eukaryotes

    • Mitosis creates genetically identical cells.
    • The diploid chromosome number is maintained.
    • Meiosis halves the chromosome number (from diploid to haploid).
    • Meiosis generates genetic variation for sexual reproduction.

    DNA Replication for Mitosis and Meiosis

    • DNA replication is necessary before mitosis/meiosis.
    • It ensures that each daughter cell receives a complete set of genetic information.
    • Chromosomes, initially long strands of DNA, condense into visible structures during cell division.
    • Each chromosome duplicates (during interphase) and becomes two sister chromatids.
    • Cohesin loops hold chromatids together until anaphase.

    Chromosome Condensation and Movement

    • Chromosomes condense to become easier to move during cell division (mitosis/meiosis).
    • Microtubules are used in the structure of the spindle which separates the chromosomes in mitosis/meiosis.
    • Kinetochores, protein structures on chromosomes, link chromosomes to microtubules.

    Mitosis Phases

    • Mitosis is divided into interphase (preceding mitosis), prophase, metaphase, anaphase, and telophase.
    • Key events like chromosome condensation, alignment at the cell equator, separation of chromatids, and nuclear membrane reformation occur in each.

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