Cancer Biology Quiz 10th Class

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Questions and Answers

Which of the following is a primary function of tumor suppressor genes?

  • Manufacturing growth factors to stimulate cell proliferation.
  • Repairing DNA damage and inducing apoptosis. (correct)
  • Accelerating cell division to promote growth.
  • Preventing cells from entering the cell cycle.

What is the primary consequence of a mutation in the p53 gene?

  • Uncontrolled cell division due to a loss of apoptosis and damaged cell removal. (correct)
  • Enhanced DNA repair mechanisms, preventing mutations from affecting the cell.
  • Increased production of tumor suppressor proteins, leading to excessive cell growth.
  • Normal regulation of the cell cycle, with no significant effect on cell proliferation.

How do cancer cells typically differ from normal cells in terms of their cell cycle control?

  • They manufacture their own growth factors, have abnormalities, and do not stop dividing at normal checkpoints. (correct)
  • They undergo controlled cell division with enhanced DNA repair mechanisms.
  • They stop dividing when growth factors are depleted, and they stop at normal checkpoints.
  • They are more sensitive to external growth factors and halt at cell cycle checkpoints.

Which checkpoint protein is directly involved in targeting cells with severe DNA damage for programmed cell death?

<p>p53 protein (C)</p> Signup and view all the answers

What is a crucial reason why cell cycle checkpoints are important?

<p>They allow for the proper regulation of cell growth and prevent excessive cell division. (A)</p> Signup and view all the answers

What is the primary function of condensins in cell division?

<p>To promote chromosome condensation (D)</p> Signup and view all the answers

Which term describes a cell that contains only one set of chromosomes?

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

Which type of cell division results in daughter cells with the same number of chromosomes as the parent cell?

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

What are the reproductive cells that are produced by the ovaries and testes?

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

What is the primary function of cell division in single-celled eukaryotes like an amoeba?

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

How many chromosomes are typically found in a human daughter cell after mitosis?

<p>46 (B)</p> Signup and view all the answers

During which phase of the cell cycle is the genome replicated?

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

What are the protein structures on chromosomes where microtubules attach during cell division?

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

What is the main characteristic of the daughter cells resulting from cell division?

<p>They are genetically identical to the parent cell (C)</p> Signup and view all the answers

Which process do prokaryotic cells use to multiply?

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

What is the name given to the two identical copies of a chromosome that are connected by a centromere?

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

Which of the following is NOT a function of cell division in multicellular organisms?

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

What is the interphase of the cell cycle responsible for?

<p>Normal cell activity and growth (D)</p> Signup and view all the answers

What are the two main phases of the cell cycle?

<p>Interphase and Mitotic phase (B)</p> Signup and view all the answers

What is the main purpose of the G2 phase of the cell cycle?

<p>Secondary cell growth, preparing for division (D)</p> Signup and view all the answers

How many chromosomes are present in normal human diploid cells?

<p>46 (B)</p> Signup and view all the answers

What is the primary function of kinetochores?

<p>To serve as points of attachment for microtubules. (D)</p> Signup and view all the answers

During which phase of the cell cycle does DNA exist in an uncondensed state, as chromatin?

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

What occurs during the prophase stage of mitosis?

<p>Chromosomes condense and become visible. (A)</p> Signup and view all the answers

What are the 'asters' referenced in the content?

<p>Radial arrays of microtubules extending from centrosomes. (C)</p> Signup and view all the answers

At which phase of mitosis are the chromosomes aligned along the central plate of the cell?

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

Which event defines anaphase in mitosis?

<p>Separation of sister chromatids. (B)</p> Signup and view all the answers

What structure is responsible for segregating the chromosomes during mitosis?

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

During which phase of the cell cycle does the replication of centrosomes occur?

<p>G2 Phase of Interphase (B)</p> Signup and view all the answers

During metaphase, where do the centromeres of the chromosomes align?

<p>At the metaphase plate (B)</p> Signup and view all the answers

What is the primary function of the microtubules during metaphase?

<p>To attach kinetochores to opposite poles (C)</p> Signup and view all the answers

What is the 'spindle' in the context of cell division?

<p>The entire apparatus of microtubules that guide chromosome movement (B)</p> Signup and view all the answers

What is a characteristic of telophase?

<p>Two new nuclear envelopes begin to form. (B)</p> Signup and view all the answers

What is the result of mitosis?

<p>One nucleus splitting into two genetically identical nuclei (A)</p> Signup and view all the answers

What may likely cause abnormalities in cell division?

<p>Chromosomal, genetic, environmental, or a combination of these factors (A)</p> Signup and view all the answers

What generally happens when there are major abnormalities in autosomal chromosomes?

<p>They usually lead to spontaneous abortion of the fetus (D)</p> Signup and view all the answers

What is the main role of the cell cycle control system?

<p>To direct the distinct events of the cell cycle. (D)</p> Signup and view all the answers

What is the primary function of cyclin-dependent kinases (Cdks) in the cell cycle?

<p>To phosphorylate target proteins, thereby activating or deactivating them. (A)</p> Signup and view all the answers

Which of the following best describes the role of cyclins in the cell cycle?

<p>Their levels fluctuate cyclically and are required for Cdk activation. (B)</p> Signup and view all the answers

What is the main function of the anaphase-promoting complex (APC)?

<p>To mark proteins such as cyclins for degradation, which leads to anaphase initiation. (D)</p> Signup and view all the answers

What mechanism is used by cells to give the cell cycle directionality?

<p>The irreversible proteolysis of specific regulatory proteins. (C)</p> Signup and view all the answers

Which of the following best characterizes the effect of growth factors on cell division?

<p>They trigger signal transduction pathways, which can lead to cell division. (D)</p> Signup and view all the answers

At which of these checkpoints in the cell cycle is DNA damage assessed?

<p>Both at the G1 and G2 checkpoints (A)</p> Signup and view all the answers

Which of the following best describes the function of cyclin-dependent kinase inhibitors (CKIs)?

<p>They selectively inhibit the kinase activity of Cdks. (C)</p> Signup and view all the answers

Which of the following criteria is NOT typically evaluated at a cell cycle checkpoint?

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

Flashcards

Cell Division

The process by which cells divide and create genetically identical copies of themselves.

Cell Cycle

The series of events that takes place between cell divisions, including growth and DNA replication.

Interphase

The first phase of the cell cycle, where the cell grows and is preparing to duplicate its DNA (genome).

G1 Phase

The part of interphase where the cell grows in size and produces proteins and organelles.

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S Phase

The part of interphase where the cell replicates its DNA (genome), ensuring each daughter cell gets a full set.

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G2 Phase

The part of interphase where the cell continues to grow and prepare for mitosis.

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Mitosis

The stage of the cell cycle where the nucleus divides into two identical daughter nuclei, creating two new cells.

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Cytokinesis

The process of dividing the cytoplasm and organelles to create two complete daughter cells after mitosis is complete.

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Somatic Cells

Cells that are not involved in sexual reproduction, such as skin, muscle, and nerve cells.

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Gametes

Specialized cells involved in sexual reproduction that have half the number of chromosomes compared to somatic cells.

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Haploid

A cell with a single set of chromosomes, resulting from meiosis.

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Condensins

A specialized protein complex that helps compact and condense chromosomes, preparing them for duplication.

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Centromere

The point on a chromosome where sister chromatids are joined.

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Sister Chromatids

The two identical copies of a chromosome that are held together at the centromere.

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Metaphase

The stage in mitosis where chromosomes align in the middle of the cell, forming a plane equidistant from the spindle poles. Sister chromatids are attached to opposing spindle poles via kinetochore microtubules.

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Metaphase Plate

An imaginary plane in the middle of the cell where chromosomes align during metaphase.

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Spindle

The structure that forms during mitosis, made up of microtubules, that helps to separate chromosomes.

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Telophase

The final stage of mitosis, where the nuclear envelope re-forms and the chromosomes decondense.

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Abnormalities of Cell Division

Errors in cell division that can lead to abnormal cell growth and cancer.

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Kinetochores

Protein discs located on the centromere of a chromosome. They serve as attachment points for microtubules during cell division.

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Prophase

The first stage of mitosis, where the chromatin condenses into visible chromosomes, the nucleolus disappears, and the mitotic spindle begins to form.

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Anaphase

The third stage of mitosis, where the sister chromatids separate and move towards opposite poles of the cell, pulled by the shortening microtubules.

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Cell Cycle Checkpoint

A critical control point in the cell cycle where signals regulate the cycle. Three major checkpoints are found in the G1, G2, and M phases.

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Control Molecules

Molecules that trigger and coordinate key events in the cell cycle. Their abundance and activity fluctuate rhythmically, pacing the cycle.

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Cyclin-Dependent Kinase (CDK)

A type of protein kinase that becomes activated by binding to a cyclin protein. Levels of cyclins fluctuate cyclically, controlling the activity of CDKs.

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Cyclin-Dependent Kinase Inhibitors (CKIs)

Proteins that bind to CDKs and cyclins, selectively inhibiting their kinase activity. Examples include p21, p27, and p16.

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Anaphase-Promoting Complex (APC)

A complex of proteins activated during mitosis to initiate anaphase. It marks target proteins (like cyclins A and B) for degradation by the 26S proteasome.

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Growth Factors

Proteins released by one group of cells that stimulate other cells to divide. For example, PDGF produced by platelets can trigger fibroblast division.

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Proteolysis

The irreversible process of breaking down proteins, utilized by cells to give the cell cycle directionality.

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Signal Transduction Pathway

A signal transduction pathway initiated by growth factors, leading to cell division. It involves tyrosine-kinase receptors and a series of signaling events.

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What is Cdk?

A type of protein kinase that regulates the cell cycle by activating proteins involved in cell division. It requires the presence of a cyclin protein to be active.

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What are Cyclins?

A class of proteins that regulate the cell cycle by binding to and activating Cdk proteins. They fluctuate in concentration throughout the cell cycle.

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What is the G2 Checkpoint?

A crucial checkpoint in the cell cycle that ensures the DNA is properly replicated before entering mitosis (M-phase). A failure at this checkpoint could lead to cell death or uncontrolled cell division.

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What is p53?

A tumor suppressor gene that plays a critical role in preventing cancer by initiating cell cycle arrest, DNA repair and apoptosis (programmed cell death) in response to DNA damage. Mutations in the p53 gene can lead to uncontrolled cell division and cancer development.

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What are Tumor Suppressor Genes?

Genes that normally prevent uncontrolled cell growth by regulating cell cycle checkpoints and promoting DNA repair. They act like brakes on cell division.

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Study Notes

Cell Division and Cell Cycle

  • Cell division is a crucial part of the cell cycle
  • It produces genetically identical daughter cells
  • Cells duplicate their genetic material before dividing, ensuring each daughter cell receives an exact copy of the DNA
  • Cell division serves different functions:
    • Reproduction (e.g., amoeba)
    • Growth and development (e.g., embryo development)
    • Tissue renewal (e.g., blood cell production)

DNA

  • DNA is the genetic information (genome)
  • It is packaged into chromosomes

Phases of the Cell Cycle

  • The cell cycle consists of interphase and the mitotic phase
    • Interphase is the normal cell activity phase
    • The mitotic phase is the cell division phase
  • Interphase includes
    • G1 phase: primary growth
    • S phase: genome replication
    • G2 phase: secondary growth
  • The mitotic phase includes mitosis and cytokinesis
    • Mitosis is the nucleus division
      • Prophase
      • Metaphase
      • Anaphase
      • Telophase
    • Cytokinesis is the cytoplasm division

Mitosis and Meiosis

  • All normal cells have 46 chromosomes (diploid cells)
  • Mitosis results in daughter cells with 46 chromosomes
  • Meiosis produces haploid gametes (sperm and egg cells) with only one set of chromosomes

Two Fundamental Cell Types

  • Prokaryotic cells (bacteria) multiply by binary fission
  • Eukaryotic cells have more complex structures

Packing for the Move

  • Condensin proteins help chromosomes condense for duplication

Structure of a Eukaryotic Chromosome

  • A chromosome has an arm, a centromere, and sister chromatids
  • Sister chromatids are duplicated chromosomes

Metaphase Chromosome

  • The centromere is a constricted region of a chromosome
  • Kinetochores are protein discs in the centromere, important for chromosome movement during cell division

Eukaryotic Cell Cycle

  • The eukaryotic cell cycle has two major phases:
    • DNA uncondensed phase (chromatin)
    • Condensation phase (chromosomes)
      • 4 stages of mitosis, cytokinesis
  • Major events to happen in the cycle

Mitosis Stages

  • Prophase: chromosomes condense, nucleoli disappear
  • Metaphase: chromosomes align at the metaphase plate
  • Anaphase: sister chromatids separate
  • Telophase: chromosomes decondense, two nuclei are formed
  • Cytokinesis: cytoplasm divides forming two new cells

Mitotic Division of an Animal Cell

  • Stages are visualized showing the changes in the cells
  • The division is visible from Metaphase, Anaphase, to Telophase including Cytokinesis

G2 of Interphase

  • Centrosomes are replicated from one
  • Animal cells have centrioles inside centrosomes
  • Chromosomes are duplicated during S phase, but not condensed

Prophase

  • Chromatin becomes more tightly coiled
  • Nucleoli disappear
  • Chromosome becomes visible
  • Sister chromatids pair up
  • Mitotic spindle starts to form

Metaphase

  • Chromosomes align at the metaphase plate
  • Centrosomes are at opposite poles
  • Sister chromatid are attached to spindle fibers

Telophase

  • Chromosomes decondense
  • Nuclear envelopes reform
  • Nucleoli reappear
  • Two daughter nuclei formed

Cells Divide at Different Rates

  • Cell division rates vary based on cell type and need
  • Different cell types have different life spans
  • Some cells are not likely to divide (Go state)

Abnormalities of Cell Division

  • Chromosomal or genetic factors, environmental factors, or a combination can cause abnormalities in cell division
  • Major chromosomal abnormalities can result in miscarriage
  • Problems in cell division can lead to abnormal chromosome numbers, which can cause developmental problems or cancer
  • Uncontrolled cell proliferation can lead to cancer

Regulation of the Cell Cycle

  • The distinct events of the cycle are controlled by a specific control system
  • The cell cycle control has checks at specific stages
  • Regulated by external and internal factors

The "Cell Cycle"

  • Checkpoints are critical control points
  • Three major checkpoints: G1, G2, and M phases
  • Cyclin-dependent kinases (Cdks) control the cell cycle

Cyclin-dependent Kinases (Cdks)

  • These are proteins that regulate cell cycle progression
  • Cdk activity is dependent on cyclins.
  • Cyclin-CDK complexes fluctuate cyclically
  • Various kinds of Cyclin-CDKs

Cyclin Dependent Kinase Inhibitors (CKIS)

  • These proteins regulate cell cycle by inhibiting some CDKs
  • CKI's are essential for cell cycle regulation

The "Cell Cycle" (external factors)

  • External factors influence the cell cycle
  • Examples - Growth factors (e.g., PDGF) stimulating cell division

Cyclin/CDK type

  • Specific cyclin/CDK combinations control different cell cycle phases

The Nobel Prize in Physiology or Medicine 2001

  • Awarded for discoveries about key cell cycle regulators

Three Main Checkpoints in the Cell Cycle

  • Checkpoints ensure correct cell size, DNA replication, and spindle fiber formation
  • The G1 checkpoint: Is the cell the correct size? Is DNA damaged?
  • The G2 checkpoint: Is DNA fully replicated? Is DNA damage repaired?
  • The M checkpoint: Have spindle fibers formed? Have they attached to chromosomes correctly?

Checkpoint Control of Cell Cycle

  • Cyclin-dependent kinases (Cdks) regulate checkpoints

Role of p53 in Cell Cycle Control (G1)

  • p53 regulates cell-cycle arrest and apoptosis in response to DNA damage
  • p53 targets cells with severe DNA damage to stimulate apoptosis process

Tumor Suppressor Genes

  • Genes that slow down cell division, repair DNA, or trigger apoptosis.
  • Their dysfunction can lead to uncontrolled cell growth and cancer development

Cancer

  • Cancer cells divide uncontrollably because they are independent of the body's growth regulation
  • Growth factors not needed, have own production, or problems in the cell cycle control system cause unregulated cell division.
  • Cancer cells stop dividing at random, not at proper checkpoints

Checkpoint Control of Cell Cycle

  • Various proteins are involved in cell-cycle control

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