Eukaryotic Chromosomes and Chromatin
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Eukaryotic Chromosomes and Chromatin

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Questions and Answers

What is the role of the cell cycle control system?

  • To enhance cellular metabolism.
  • To regulate the sequential events of the cell cycle. (correct)
  • To increase the size of the cell.
  • To facilitate transcription of RNA.

    • During which phase does the synthesis of DNA and duplication of chromosomes occur?

  • G1 Phase
  • G2 Phase
  • S Phase (correct)
  • M Phase

    • What happens to a cell in the G0 phase?

  • It prepares for mitosis.
  • It actively divides.
  • It becomes inactive and performs other cellular duties. (correct)
  • It only replicates its DNA.

    • What triggers the cell cycle to move past checkpoints?

    <p>Go-ahead signals.</p> Signup and view all the answers

    What characterizes the G2 phase of the cell cycle?

    <p>The cell reorganizes contents for mitosis.</p> Signup and view all the answers

    How is the cell cycle controlled?

    <p>Through an internal clock mechanism and external signals.</p> Signup and view all the answers

    Why is the cell cycle considered highly regulated?

    <p>To ensure accurate duplication and distribution of genetic material.</p> Signup and view all the answers

    What distinguishes the G1 phase of the cell cycle?

    <p>Proteins and organelles are synthesized.</p> Signup and view all the answers

    What is the primary structure that makes up eukaryotic chromosomes?

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

    When do chromosomes form during the cell cycle?

    <p>During cell division</p> Signup and view all the answers

    What is the role of cohesins in a duplicated chromosome?

    <p>To attach chromatids at the centromere</p> Signup and view all the answers

    What is the diploid number of chromosomes in humans?

    <p>46 chromosomes</p> Signup and view all the answers

    What happens to chromatids during cell division?

    <p>They separate into two nuclei</p> Signup and view all the answers

    What defines a haploid cell?

    <p>Contains one set of chromosomes</p> Signup and view all the answers

    Where are haploid cells typically found in humans?

    <p>In gametes</p> Signup and view all the answers

    What occurs to chromatin at the end of cell division?

    <p>It becomes less highly organized</p> Signup and view all the answers

    What is the primary role of the M Phase Checkpoint in the cell cycle?

    <p>To confirm all chromosomes are attached to the spindle</p> Signup and view all the answers

    Which factor can cause a cell to enter a resting state known as G0?

    <p>Insufficient growth factors</p> Signup and view all the answers

    What happens during the G2 Checkpoint?

    <p>The integrity of the DNA and attachment of sister chromatids is checked</p> Signup and view all the answers

    Why is it important for damaged DNA not to be passed onto daughter cells?

    <p>It prevents mutation accumulation and cancer development</p> Signup and view all the answers

    What triggers the cell to pause mitosis?

    <p>Straggler chromosomes floating in the cytoplasm</p> Signup and view all the answers

    What is the consequence of not receiving positive signals at the G1 Checkpoint?

    <p>The cell may enter a non-dividing state</p> Signup and view all the answers

    What does the spindle checkpoint ensure before anaphase begins?

    <p>All chromosomes are aligned along the metaphase plate</p> Signup and view all the answers

    What is referred to as 'straggler' chromosomes?

    <p>Chromosomes that are out of the typical alignment</p> Signup and view all the answers

    What is the role of cyclins in cell cycle regulation?

    <p>Cyclins regulate the activity of CDKs by varying their concentration.</p> Signup and view all the answers

    What is MPF and its significance in the cell cycle?

    <p>MPF promotes the transition from G2 to M phase by phosphorylating specific proteins.</p> Signup and view all the answers

    How do growth factors influence the cell cycle?

    <p>They are released by specific cells to trigger division in other cells.</p> Signup and view all the answers

    What does anchorage dependence refer to in cell division?

    <p>Cells must be anchored to a substratum to successfully undergo division.</p> Signup and view all the answers

    What occurs when the cyclin-CDK complex has fulfilled its role?

    <p>It is targeted for degradation and destruction.</p> Signup and view all the answers

    In density-dependent inhibition, what happens to crowded cells?

    <p>They stop dividing when they become too crowded.</p> Signup and view all the answers

    What characterizes cancer cells compared to normal cells?

    <p>Cancer cells do not adhere to the body's control mechanisms for division.</p> Signup and view all the answers

    What is one main factor that determines the number of cells in a tissue?

    <p>The balance between cell division and cell death.</p> Signup and view all the answers

    Why are older people more commonly affected by cancer?

    <p>Cancer can develop after many rounds of cell divisions.</p> Signup and view all the answers

    What does it mean to be predisposed to cancer?

    <p>Being born with a mutation that increases cancer risk.</p> Signup and view all the answers

    What is a primary cancer?

    <p>The original tumor from which cancer cells spread.</p> Signup and view all the answers

    What is the main route by which cancer cells spread to distant organs?

    <p>Via blood or lymph circulation.</p> Signup and view all the answers

    What is referred to as metastasis in the context of cancer?

    <p>The spreading of cancers to non-adjacent organs.</p> Signup and view all the answers

    Why do cancer cells often spread to the lungs?

    <p>The pulmonary capillaries are often where vessels narrow.</p> Signup and view all the answers

    What generally happens to cancer cells as they travel through the lymphatic system?

    <p>They get stuck in the nearest lymph nodes.</p> Signup and view all the answers

    What is a consequence of removing nearby lymph nodes during tumor removal?

    <p>It minimizes the chances of cancer cells spreading to lymph nodes.</p> Signup and view all the answers

    Study Notes

    Chromosomes and Chromatin

    • Eukaryotic chromosomes are composed of chromatin, a DNA-protein complex.
    • Chromatin condenses during cell division, resulting in visible chromosomes.
    • Chromosomes are only formed when cells divide, disappearing during non-dividing phases.

    Chromosome Structure

    • DNA is replicated during cell division, leading to the formation of two sister chromatids.
    • Sister chromatids are connected at the centromere, where they are most closely attached.
    • Haploid cells contain one set of chromosomes (n=23 in humans, found in gametes).
    • Diploid cells contain two sets of chromosomes (2n=46 in humans, found in somatic cells).

    Cell Cycle Overview

    • The cell cycle includes stages for growth and division, regulated to ensure accurate DNA distribution.
    • G1 (First Gap): Initial growth and organelle production.
    • S phase: DNA synthesis and chromosome duplication.
    • G2 (Second Gap): Further growth and preparation for mitosis.
    • G0 (Resting State): Non-dividing cells performing normal functions, can be reversible or permanent.

    Cell Cycle Control Points

    • The cell cycle is directed by a control system with specific checkpoints for progression.
    • Checkpoints assess DNA integrity and proper chromosome attachment before division.
    • M Phase Checkpoint: Ensures chromatids are correctly attached to spindle fibers before anaphase begins.

    Regulatory Proteins

    • Two primary types control the cell cycle: Cyclins and Cyclin-dependent Kinases (Cdks).
    • Cdks activate when bound to cyclins, with their activity fluctuating based on cyclin concentration.
    • MPF (maturation-promoting factor) is a cyclin-Cdk complex that facilitates the transition from G2 to M phase.

    Cancer Cells Characteristics

    • Cancer cells bypass normal regulatory signals, leading to uncontrolled growth.
    • Mutations can predispose individuals to develop cancer, often discovered over multiple cell divisions.
    • Cancer cells can invade nearby tissues (local spread) and disseminate to distant sites via blood or lymph (systemic spread).
    • Metastasis involves primary cancer cells establishing new tumors in separate organs, commonly in the lungs or lymph nodes.

    Metastasis Process

    • Cancer cells may break from the primary tumor and enter circulation through blood or lymph vessels.
    • They typically immobilize at the first narrow passage, such as in lung capillaries or lymph nodes, leading to secondary tumor formation.

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    Description

    This quiz explores the structure and function of eukaryotic chromosomes, focusing on chromatin's role during cell division. Understand how DNA and protein complexes condense to form visible chromosomes under a microscope. Test your knowledge about the dynamics of chromatin and the presence of chromosomes.

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