Cell Growth and Division Overview

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Questions and Answers

What role does the p53 gene play in cancer development?

  • It enhances anchorage dependence.
  • It inhibits DNA damage response.
  • It promotes cell division.
  • It acts as a tumor suppressor. (correct)

Which of the following best describes a proto-oncogene?

  • A gene that suppresses tumor formation.
  • A gene responsible for anchorage dependence.
  • A gene that drives normal cells to become cancerous when mutated. (correct)
  • A gene that causes excessive cell death.

What characteristic do cancer cells possess regarding density-dependent inhibition?

  • They are free from density-dependent inhibition. (correct)
  • They are responsive to cell density changes.
  • They undergo density-dependent apoptosis.
  • They grow more slowly than normal cells.

How does the process of cytokinesis differ in plant cells compared to animal cells?

<p>Plant cells synthesize a new cell wall at the cell plate. (D)</p> Signup and view all the answers

What is a common cause of cancer related to external environmental factors?

<p>Viral infections. (C)</p> Signup and view all the answers

What is the primary goal of mitosis and cell division?

<p>To facilitate growth, repair, and development (D)</p> Signup and view all the answers

Which phase of interphase is characterized by the synthesis of new proteins and organelles?

<p>G1 Phase (A)</p> Signup and view all the answers

What happens during the S phase of interphase?

<p>Chromosomes are replicated (A)</p> Signup and view all the answers

Which of the following most directly controls the cell cycle?

<p>Cyclins and CDKs (C)</p> Signup and view all the answers

Density-dependent inhibition primarily influences what aspect of cell behavior?

<p>Cell cycle progression (B)</p> Signup and view all the answers

What is the role of growth factors in regulating the cell cycle?

<p>They promote cell division in response to external signals (C)</p> Signup and view all the answers

What characterizes a malignant tumor?

<p>It may invade surrounding tissues or spread around the body (B)</p> Signup and view all the answers

What occurs to chromatin before mitosis begins?

<p>It condenses into chromosomes (D)</p> Signup and view all the answers

What is the primary purpose of mitosis in eukaryotic organisms?

<p>To create two genetically identical daughter cells (C)</p> Signup and view all the answers

During which phase does the nuclear envelope reform around the sets of chromosomes?

<p>Telophase (D)</p> Signup and view all the answers

What major event occurs during metaphase?

<p>Chromosomes align along the metaphase plate (C)</p> Signup and view all the answers

Which structure is responsible for pulling apart sister chromatids during anaphase?

<p>Spindle fibers (C)</p> Signup and view all the answers

What initiates the process of cytokinesis in animal cells?

<p>Development of a cleavage furrow (D)</p> Signup and view all the answers

What is the outcome if errors occur during mitosis?

<p>Development of mutations and genetic disorders (A)</p> Signup and view all the answers

Which phase is characterized by spindle fibers attaching to the kinetochores of chromosomes?

<p>Metaphase (C)</p> Signup and view all the answers

What happens to chromatin at the beginning of mitosis?

<p>It condenses into visible chromosomes (B)</p> Signup and view all the answers

Flashcards

Mitosis

The process by which a single cell divides into two identical daughter cells.

Interphase

The time period between cell divisions, where the cell grows and carries out its normal functions.

G1 Phase

The phase of interphase where the cell increases in size, synthesizes proteins, and grows organelles.

S Phase

The phase of interphase where DNA replication occurs, creating an identical copy of the cell's genetic material.

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G2 Phase

The phase of interphase where the cell prepares for mitosis by producing organelles and molecules needed for cell division.

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Cyclins

Proteins that regulate the cell cycle, controlling the progression of the cell cycle.

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CDK's (Cyclin dependent kinases)

Enzymes that activate cyclins, ultimately controlling the cell cycle.

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External Regulators

Factors that influence the cell cycle from outside the cell, such as growth factors.

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Tumor Suppressor Gene

A gene that normally suppresses tumor growth, but when mutated, can contribute to cancer development.

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Proto-oncogene

A gene that, when mutated, can promote the development of cancer by increasing cell proliferation.

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p53 Gene

A tumor suppressor gene that is frequently mutated in various cancers. It plays a critical role in DNA damage repair and cell cycle control.

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Density-dependent Inhibition

The ability of normal cells to stop dividing when they come into contact with each other.

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Anchorage Dependence

The requirement of normal cells to be attached to a solid surface to divide.

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What is mitosis?

The process where a single cell divides into two genetically identical daughter cells, crucial for growth, repair and asexual reproduction in eukaryotic organisms.

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What happens in nuclear division?

A type of cell division where the nucleus divides into two identical nuclei, ensuring each daughter cell receives a complete set of chromosomes.

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What happens in prophase?

The first stage of mitosis where chromatin condenses into visible chromosomes, the nuclear envelope breaks down, and spindle fibers form from microtubules emanating from the centrosomes.

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What happens in metaphase?

The second stage of mitosis where chromosomes line up along the metaphase plate, an imaginary plane equidistant from the two poles, ensuring each daughter cell receives an identical copy of each chromosome.

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What happens in anaphase?

The third stage of mitosis where sister chromatids separate at the centromere and spindle fibers pull them towards opposite poles, ensuring each daughter cell receives a complete set of chromosomes.

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What happens in telophase?

The final stage of mitosis where chromosomes reach opposite poles, decondense, and a nuclear envelope reforms around each set of chromosomes, spindle fibers disassemble and nucleoli reappear.

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What is cytokinesis?

The division of the cytoplasm that typically begins during late anaphase or telophase. In animals, a cleavage furrow forms, while in plants, a cell plate forms.

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Why is mitosis important?

A vital process for growth, development, tissue repair, and asexual reproduction. It ensures that cells have the correct number of chromosomes for proper functioning.

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Study Notes

Cell Growth and Division

  • The goal of mitosis and cell division is growth, repair, and development.
  • Cell size is limited by the surface area-to-volume ratio, affecting nutrient intake and waste removal.
  • DNA overload is another limitation as cells grow larger.
  • Interphase: A crucial stage preceding mitosis.
    • G1 Phase: Cell growth, protein synthesis, and organelle production. Longest stage.
    • S Phase: DNA replication, creating identical chromosome copies.
    • G2 Phase: Organelle duplication, producing molecules needed for division; crucial checkpoint before mitosis begins.
  • Chromosomes: Condensed chromatin (DNA and proteins).
  • Chromosome Replication: Before division, chromosomes replicate forming identical copies.
  • Mitosis Phases:
    • Prophase: Chromatin condenses to visible chromosomes; each chromosome consists of two sister chromatids joined at the centromere. The nuclear envelope breaks down and the nucleolus disappears. Spindle fibers form from microtubules, emanating from centrosomes. Centrosomes move to opposite poles of the cell.
    • Metaphase: Spindle fibers attach to kinetochores of chromosomes. Chromosomes align along the metaphase plate, equidistant from the two poles. This alignment ensures each daughter cell receives an identical copy of each chromosome.
    • Anaphase: Sister chromatids separate at the centromere, becoming independent chromosomes. Spindle fibers pull separated chromosomes to opposite poles. This ensures each daughter cell receives a complete set of chromosomes.
    • Telophase: Chromosomes reach opposite poles; they begin to decondense. A nuclear envelope reforms around each set of chromosomes. Spindle fibers disassemble. Nucleoli reappear in each daughter nucleus.
  • Cell Cycle Regulation:
    • Internal Regulation: Cyclins and Cyclin-Dependent Kinases (CDKs) regulate the cycle's progression.
    • External Regulation: Growth factors, density-dependent inhibition, and anchorage dependence influence cell division.
      • Cells divide in response to signals (e.g., growth factors) and stop dividing when they are crowded.
      • Cells usually need to be attached to a substratum to divide.
  • Cancer: Uncontrolled Cell Growth
    • Tumors: Masses of abnormal cells.
      • Benign: Do not invade or spread.
      • Malignant: Invade and spread, causing cancer.
    • Causes: Various factors like smoking, radiation, viral infections, genetics, and carcinogens.
    • Key aspect: Disrupted cell cycle control.
    • p53: A tumor suppressor gene crucial for detecting and preventing cell division with damaged DNA; significant role in cancer suppression.
    • Proto-oncogenes: Genes which, when mutated, can turn normal cells into cancerous ones. A well-studied proto-oncogene is Ras.
  • Cytokinesis: Cell division
    • Plant cells form a cell plate, synthesized from vesicles, to create new cells.
    • Animal cells form a cleavage furrow to pinch the cell membrane in two.
  • Importance of Mitosis:
    • Maintains correct chromosome number for proper cell function.
    • Crucial for growth, development, tissue repair, and asexual reproduction.
    • Errors in mitosis can lead to mutations and genetic disorders.

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