Eukaryotic Cell Division

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Questions and Answers

What is the primary purpose of mitosis in eukaryotic cells?

  • To create spores
  • To generate gametes
  • To produce daughter cells with the same chromosomal number (correct)
  • To reduce the chromosomal number

Meiosis I is similar to mitosis.

False (B)

What are the three main phases of interphase?

G1, S, G2

In _____, homologous chromosomes are separated and distributed to daughter cells.

<p>meiosis I</p> Signup and view all the answers

Which of the following phases is NOT part of interphase?

<p>Mitosis (A)</p> Signup and view all the answers

Match the type of cell division with its description:

<p>Mitosis = Equational division producing identical daughter cells Meiosis = Reductional division resulting in gametes or spores Amitosis = Simple form of cell division without mitotic spindles Interphase = Preparation phase before cell division</p> Signup and view all the answers

Amitosis is a more typical form of cell division in eukaryotes.

<p>False (B)</p> Signup and view all the answers

What is the role of checkpoints during interphase?

<p>To allow the cell to advance or halt development based on conditions</p> Signup and view all the answers

What does asymmetric cell division result in?

<p>Daughter cells with different amounts of fate-determining molecules (B)</p> Signup and view all the answers

Cytokinesis in plants and animals occurs in exactly the same way.

<p>False (B)</p> Signup and view all the answers

In which phase does cytokinesis occur in Fission yeast (S.pombe)?

<p>G1 phase</p> Signup and view all the answers

The first discovery of cell division in aquatic plants was made by __________.

<p>Barthélemy Charles Joseph Dumortier</p> Signup and view all the answers

Match the following scientists to their contributions to cell division:

<p>Kurt Michel = Filmed cell division for the first time Hugo von Mohl = Described plant cell division in detail Robert Remak = Confirmed animal cell division Franz Julius Ferdinand Meyen = Documented cell division at root tips of plants</p> Signup and view all the answers

What did Hugo von Mohl detail in his PhD thesis?

<p>Plant cell division (B)</p> Signup and view all the answers

Barthélemy Charles Joseph Dumortier was the first to discover cell division.

<p>True (A)</p> Signup and view all the answers

Which year did Kurt Michel film cell division for the first time?

<p>1943</p> Signup and view all the answers

In animals, cytokinesis ends with the formation of a __________ and subsequent cleavage.

<p>contractile ring</p> Signup and view all the answers

What hypothesis about cell proliferation was proposed in the early 19th century?

<p>Cells proliferate by the attachment of new cells (D)</p> Signup and view all the answers

What is checked at the G2 checkpoint?

<p>Cell size and DNA replication (B)</p> Signup and view all the answers

The M phase can only be mitosis and never meiosis.

<p>False (B)</p> Signup and view all the answers

What is the primary role of cyclins in the cell cycle?

<p>To regulate the progression of the cell cycle by activating cyclin-dependent kinases.</p> Signup and view all the answers

During prophase, long strands of chromatin condense to form _____ visible strands called chromosomes.

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

Which of the following occurs during anaphase?

<p>Sister chromatids separate and are pulled to opposite poles (D)</p> Signup and view all the answers

Cytokinesis results in the separation of two daughter cells.

<p>True (A)</p> Signup and view all the answers

What protein is important for crossing over during meiosis?

<p>Spo11</p> Signup and view all the answers

In metaphase, chromosomes align on the _____ plate.

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

Match the following stages of cell division with their descriptions:

<p>Prophase = Chromatin condenses into chromosomes Anaphase = Sister chromatids are pulled apart Telophase = Nuclear envelope reforms Cytokinesis = Cytoplasmic division occurs</p> Signup and view all the answers

What marks the transition from metaphase to anaphase?

<p>The activation of the anaphase-promoting complex (D)</p> Signup and view all the answers

The centromeres of the chromosomes align on the metaphase plate during telophase.

<p>False (B)</p> Signup and view all the answers

What is the role of cohesin proteins during cell division?

<p>To hold sister chromatids together until they are separated during anaphase.</p> Signup and view all the answers

After the chromosomes line up in the middle of the cell, the spindle fibers will _____ them apart.

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

What happens during prophase?

<p>The mitotic spindle assembles (D)</p> Signup and view all the answers

Flashcards

Eukaryotic Cell Division

Cell division process in organisms with a nucleus, including mitosis (non-reduction) and meiosis (reduction).

Mitosis

Eukaryotic cell division that results in two daughter cells with the same number of chromosomes as the parent cell.

Meiosis

Eukaryotic cell division that produces four daughter cells with half the number of chromosomes as the parent cell.

Interphase

The phase of the cell cycle where a cell grows, replicates its DNA, and prepares for mitosis or meiosis.

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Gametic Meiosis

Meiosis in animals and some other organisms producing gametes (sex cells).

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Sporic Meiosis

Meiosis in plants that produces spores, which germinate into the haploid phase.

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Chromosomes in Mitosis

In mitosis metaphase, chromosomes align in the middle of the cell, before sister chromatids separate.

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Homologous Chromosomes (Meiosis I)

Pairs of chromosomes align before separation in meiosis I; one from each parent.

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G2 Checkpoint

This checkpoint ensures the cell has grown sufficiently and that DNA replication is complete before proceeding to mitosis or meiosis.

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Metaphase Checkpoint

This checkpoint verifies that chromosomes are properly attached to the spindle fibers and aligned at the metaphase plate.

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S Phase (DNA Replication)

The stage of interphase where the cell replicates its DNA, ensuring that each daughter cell receives a complete set of chromosomes.

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Cyclin-Dependent Kinases (CDKs)

Enzymes that control the progression of the cell cycle by activating or inhibiting proteins involved in specific stages.

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Cyclin

A protein that binds to CDKs, regulating their activity and thus influencing the cell cycle.

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G1-S Transition Checkpoint

The most important checkpoint, deciding whether the cell proceeds into DNA replication (S phase) or exits the cell cycle.

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Prophase (Mitosis/Meiosis)

The first stage of cell division where the nuclear envelope breaks down, chromosomes condense, and the mitotic spindle begins to form.

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Chromosomes in Prophase

Long strands of chromatin condense into shorter, thicker, visible structures called chromosomes, visible under a microscope.

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Crossing Over (Meiosis)

The exchange of genetic material between homologous chromosomes during prophase I of meiosis, creating genetic diversity.

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Prometaphase (Mitosis/Meiosis)

The stage following prophase where the nuclear envelope breaks down completely, allowing spindle fibers to attach to chromosomes.

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Metaphase Plate (Mitosis/Meiosis)

The imaginary line along the middle of the cell where chromosomes align during metaphase, equidistant from both spindle poles.

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Anaphase (Mitosis/Meiosis)

The stage where sister chromatids are pulled apart by spindle fibers, moving towards opposite poles of the cell.

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Telophase (Mitosis/Meiosis)

The final stage of cell division where a new nuclear envelope forms around the separated chromosomes, the spindle fibers disappear, and cytokinesis begins.

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Cytokinesis

The division of the cytoplasm after mitosis or meiosis, resulting in two separate daughter cells.

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Anaphase-Promoting Complex (APC)

A protein complex that triggers the breakdown of proteins involved in the metaphase-anaphase transition, initiating the separation of chromosomes.

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Asymmetric Cell Division

Cell division where daughter cells inherit different amounts of fate-determining molecules, leading to different cell fates.

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Cytokinesis in Animals

The process of cell division in animals involves a contractile ring that pinches off the cell membrane, creating two daughter cells.

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Cytokinesis in Plants

Cell division in plants uses a cell plate that forms a new cell wall between daughter cells.

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Fission Yeast Cytokinesis

In fission yeast, cytokinesis occurs during the G1 phase of the cell cycle.

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Barthélemy Dumortier's Observation

He identified the first cell division in plants in the 1830s and described its process in simple aquatic plants.

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Hugo von Mohl's Contribution

In 1835, this German botanist provided a detailed description of cell division in algae.

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Franz Meyen's Confirmation

He confirmed the mechanism of cell division at plant root tips in 1838.

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Robert Remak's Discovery

He discovered animal cell division in chicken embryos in 1841, later confirming it in various animals.

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First Filmed Cell Division

Kurt Michel successfully filmed cell division in 1943 using a phase-contrast microscope.

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Phase-Contrast Microscope

A microscope that enhances the contrast between different parts of a transparent specimen, allowing for better visualization of cells.

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Study Notes

Eukaryotic Cell Division

  • Eukaryotic cell division is more complex than prokaryotic cell division.
  • Meiosis reduces the chromosome number.
  • Mitosis maintains the chromosome number.
  • Amitosis is a less common, atypical form.
  • Mitosis and amitosis show more diversity among organisms like protists (e.g., diatoms, dinoflagellates) and fungi.

Forms of Mitosis (Karyokinesis)

  • Closed intranuclear pleuromitosis
  • Closed extranuclear pleuromitosis

Mitotic Metaphase

  • Chromosomes (with two sister chromatids) align on the metaphase plate.
  • Sister chromatids are then separated and distributed to daughter cells.

Meiosis

  • Meiosis I: Homologous chromosomes are paired before separation.
  • Meiosis II: Similar to mitosis, chromatids are separated.
  • Gametic meiosis: Meiosis produces gametes (e.g., in humans, other higher animals).
  • Sporic meiosis: Meiosis produces spores leading to a haploid vegetative phase (gametophyte) in some organisms (especially plants).

Cell Cycle and Mitosis

  • Interphase: The period before mitosis/meiosis. Has three sub-phases:

    • G1: Cell growth and specialized functions. Checkpoints control the process.
      • 1st checkpoint: G1-S, checks size and DNA damage.
    • S: Chromosomes replicate.
    • G2: Final growth stages, synthesis of spindle fibers.
      • 2nd checkpoint: G2, checks size and complete DNA replication.
    • 3rd checkpoint: Metaphase, checks chromosome attachment to spindles.
  • M Phase: Mitosis or meiosis, followed by cytokinesis.

    • Controlled by cyclin-cyclin dependent kinase complexes.
  • Prophase: Chromosomes condense, nuclear envelope breaks down, nucleolus disappears, spindle fibers assemble. Crossing over occurs in meiosis.

  • Prometaphase: Nuclear envelope completely gone. Spindle fibers attach to kinetochores.

  • Metaphase: Chromosomes align on the metaphase plate. Cohesins hold sister chromatids.

  • Anaphase: Sister chromatids separate and move to opposite poles. This is triggered by the anaphase-promoting complex (APC) destroying proteins important to the metaphase-anaphase transition.

  • Telophase: New nuclear envelopes form around chromatin at each pole. Nucleoli reform. Chromatin returns to its relaxed state.

  • Cytokinesis: Cytoplasmic division creating two daughter cells.

  • Animal cells: Contractile ring formation and cleavage furrow.

  • Plant cells: Cell plate formation and new cell wall development.

  • Fission yeast (S. pombe): Cytokinesis in G1 phase.

History of Cell Division Discovery

  • Early hypotheses about cell proliferation existed.
  • Barthélemy Charles Joseph Dumortier (1832) described cell division in plants.
  • Hugo von Mohl (1835) provided more detailed descriptions of plant cell division.
  • Franz Julius Ferdinand Meyen (1838) confirmed cell division at root tips.
  • Robert Remak (1852) confirmed animal cell division.
  • Kurt Michel (1943) filmed cell division.

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