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The nucleus is the smallest organelle in the cell.
The nucleus is the smallest organelle in the cell.
False
The nuclear pore is a small complex of proteins that allows only large molecules to pass through.
The nuclear pore is a small complex of proteins that allows only large molecules to pass through.
False
The main function of the nucleus is to synthesize proteins.
The main function of the nucleus is to synthesize proteins.
False
Chromosomes are made up of only DNA.
Chromosomes are made up of only DNA.
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The cell cycle is a random process that occurs in cells.
The cell cycle is a random process that occurs in cells.
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Mitosis is the process of sexual reproduction in cells.
Mitosis is the process of sexual reproduction in cells.
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The cell cycle consists of three main phases: interphase, M phase, and G phase.
The cell cycle consists of three main phases: interphase, M phase, and G phase.
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Meiosis is the process of asexual reproduction in cells.
Meiosis is the process of asexual reproduction in cells.
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The G1 phase is the stage where DNA replication takes place.
The G1 phase is the stage where DNA replication takes place.
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Nerve and muscle cells typically complete the cell cycle.
Nerve and muscle cells typically complete the cell cycle.
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The G2 phase is the stage where the cell grows and accumulates nutrients.
The G2 phase is the stage where the cell grows and accumulates nutrients.
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The restriction checkpoint is the least important checkpoint in the cell cycle.
The restriction checkpoint is the least important checkpoint in the cell cycle.
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Malfunction of the checkpoints at the G1, S, and G2 phases may lead to a mitotic catastrophe.
Malfunction of the checkpoints at the G1, S, and G2 phases may lead to a mitotic catastrophe.
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Mitotic catastrophe is defined as the successful arrest of the cell cycle before mitosis.
Mitotic catastrophe is defined as the successful arrest of the cell cycle before mitosis.
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Aneuploid cells are cells containing a normal number of chromosomes.
Aneuploid cells are cells containing a normal number of chromosomes.
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A mitotic catastrophe may contribute to oncogenesis.
A mitotic catastrophe may contribute to oncogenesis.
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Mitosis always includes cytokinesis.
Mitosis always includes cytokinesis.
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The nucleolus completely disappears in early prophase.
The nucleolus completely disappears in early prophase.
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Each chromosome is attached to a spindle fiber in anaphase.
Each chromosome is attached to a spindle fiber in anaphase.
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The sister chromatids are pulled apart in metaphase.
The sister chromatids are pulled apart in metaphase.
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The spindle disappears in anaphase.
The spindle disappears in anaphase.
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Cytokinesis is the process by which the cytoplasm of the cell splits to form four independent cells.
Cytokinesis is the process by which the cytoplasm of the cell splits to form four independent cells.
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The contractile ring consists of a very thick array of actin filaments.
The contractile ring consists of a very thick array of actin filaments.
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Mitosis lasts about 2 hours.
Mitosis lasts about 2 hours.
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Study Notes
Nucleus
- The control center of the cell that controls metabolism and reproduction
- Contains DNA (genetic material) found on chromosomes
- The largest organelle, dark and round, surrounded by a double membrane called the nuclear envelope
- Nuclear pore is a large complex of proteins that allows small molecules and ions to freely pass, or diffuse, into or out of the nucleus
- Main functions include:
- Protein synthesis, cell division, and differentiation
- Controlling the synthesis of enzymes involved in cellular metabolism
- Controlling hereditary traits of the organism
Cell Cycle
- A self-regulated sequence of events that controls cell growth and cell division
- The goal of the cell cycle is to produce two daughter cells, each containing chromosomes identical to those of the parent cell
- Divided into two main types:
- Mitosis (Asexual reproduction cycle): Process in which the nucleus of a cell divides to create two new nuclei, each containing an identical copy of DNA (somatic cells)
- Meiosis (Sexual reproduction cycle): Process by which certain sex cells are created
Phases of the Cell Cycle
- Interphase:
- The cell grows at a steady rate throughout interphase
- It is the longest part of the cell cycle involving three sub-phases:
- G1 (gap1) phase: During which the cell is metabolically active and continuously grows but does not replicate its DNA
- S (synthesis) phase: During which DNA replication takes place
- G2 (gap 2) phase: During which cell growth continues and proteins are synthesized in preparation for mitosis
- M phase (Mitosis):
- The process in which the nucleus of a cell divides to create two new nuclei
- Includes both karyokinesis (division of the nucleus) and cytokinesis (division of the cell)
Cell Cycle Checkpoints
- The restriction checkpoint (or “point of no return”) is the most important checkpoint in the cell cycle
- At this checkpoint, the cell self-evaluates its own replicative potential before deciding to either enter the S phase and the next round of cell division or to retire and leave the cell cycle
- Malfunction of any of the checkpoints at the G1, S, and G2 phases of the cell cycle and the checkpoint at M phase may lead to a mitotic catastrophe
Mitosis
- Lasts about 1 hour
- Phases of Mitosis:
- Prophase: The replicated chromatin condenses and becomes visible as chromosomes
- Metaphase: Each chromatid is attached to a spindle fiber, centromeres of duplicated chromosomes are aligned at the equator
- Anaphase: The centromeres divide, and the sister chromatids of each chromosome are pulled apart and move to the opposite ends of the cell, pulled by spindle fibers attached to the kinetochore regions
- Telophase: The chromosomes become indistinct chromatin again, the spindle disappears, and the nuclear envelope and nucleolus reappear, daughter cells are forming
Cytokinesis
- The process by which the cytoplasm of the cell splits to form two independent cells
- The separation at the cleavage furrow is achieved by a contractile ring consisting of a very thin array of actin filaments positioned around the perimeter of the cell
- Many granular matrix formed by the Golgi body and endoplasmic reticulum accumulates in the equatorial region, forming a cell plate
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Description
This quiz covers the nucleus, the control center of the cell, and its role in metabolism and reproduction. It explores the structure and function of the nucleus, including DNA and chromosomes.
