Cell Cycle and Checkpoints Quiz
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Questions and Answers

What is the primary function of mitosis?

  • To synthesize proteins
  • To repair tissues only
  • To duplicate the DNA
  • To segregate chromosomes and divide the cell (correct)

    • Cytokinesis occurs only during the M phase of the cell cycle.

    True

    What is the role of the kinetochore during cell division?

    To attach chromatids to microtubules and assist in their movement to the poles of the cell.

    The __________ phase of the cell cycle includes DNA duplication.

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

    Match the following stages of mitosis with their descriptions:

    <p>Prophase = Chromatin condenses and the nuclear envelope disintegrates Metaphase = Chromosomes align at the equatorial plate Anaphase = Sister chromatids are pulled apart to opposite poles Cytokinesis = Division of the cytoplasm into two daughter cells</p> Signup and view all the answers

    Which phase of mitosis is characterized by the breakdown of the nuclear envelope?

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

    How long does the M Phase typically last?

    <p>About 1 hour.</p> Signup and view all the answers

    Sister chromatids are separated during metaphase.

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

    What happens during telophase?

    <p>A nuclear envelope reappears around the chromosomes.</p> Signup and view all the answers

    Cytokinesis occurs after the completion of mitosis.

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

    What is the chromosome number in gametes produced through meiosis?

    <p>23 chromosomes</p> Signup and view all the answers

    Gametes are described as ______ because they contain one member of each chromosome pair.

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

    Match the following terms with their definitions:

    <p>Telophase = Reconstitution of the nuclear envelope and uncoiling of chromosomes Cytokinesis = Division of the cytoplasm to form two daughter cells Meiosis = Process that results in haploid gametes Crossing-over = Exchange of chromosome segments between homologous chromosomes</p> Signup and view all the answers

    Which statement accurately describes homologous chromosomes?

    <p>They contain the same genes but may have different alleles.</p> Signup and view all the answers

    The zygote is haploid in chromosome number.

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

    What is the primary outcome of crossing-over during meiosis?

    <p>Genetic diversity</p> Signup and view all the answers

    What is the end product of meiosis in males?

    <p>Four identical haploid spermatids</p> Signup and view all the answers

    In females, the two meiotic divisions of a primary oocyte produce three functional gametes.

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

    What type of division occurs during meiosis II?

    <p>Equatorial division</p> Signup and view all the answers

    The chromosome number is reduced from diploid (2n) to __________ (1n) during meiosis I.

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

    Match the phases of meiosis I with their correct descriptions.

    <p>Prophase I = Chromosomes condense and homologous chromosomes pair Metaphase I = Paired chromosomes align at the equatorial plate Anaphase I = Homologous chromosomes segregate to opposite sides Telophase I = Formation of two haploid nuclei</p> Signup and view all the answers

    During which stage of prophase I does crossing over occur?

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

    No DNA replication occurs before meiosis II.

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

    What is a chiasma?

    <p>The point where homologous chromosomes are attached during crossing over.</p> Signup and view all the answers

    What is the primary structural form of heterochromatin?

    <p>Highly condensed structure</p> Signup and view all the answers

    Heterochromatin is transcriptionally active at all times.

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

    What is a nucleosome composed of?

    <p>DNA and histone proteins</p> Signup and view all the answers

    The basic subunit of chromatin is known as a ______.

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

    Which of the following is associated with the regulation of gene expression or chromosome integrity?

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

    Heterochromatin can influence the expression levels of adjacent genes.

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

    The term for the inheritance mechanism involving heterochromatin is ______.

    <p>epigenetic inheritance</p> Signup and view all the answers

    What is the primary function of chromatin?

    <p>To package DNA into a smaller volume</p> Signup and view all the answers

    Euchromatin is tightly packed and less accessible for transcription.

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

    What are the two types of chromatin mentioned?

    <p>Euchromatin and heterochromatin</p> Signup and view all the answers

    Chromatin is composed of DNA and _____ proteins.

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

    What percentage of the human genome is composed of euchromatin?

    <p>92%</p> Signup and view all the answers

    During interphase, chromatin is more tightly packed to prevent transcription.

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

    What structural change occurs to chromatin during mitosis?

    <p>Chromatin condenses to form chromosomes.</p> Signup and view all the answers

    Which of the following statements about euchromatin is true?

    <p>Euchromatin is involved in the active transcription of DNA.</p> Signup and view all the answers

    Heterochromatin is only found in eukaryotes.

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

    What are the two main types of heterochromatin?

    <p>Constitutive heterochromatin and facultative heterochromatin.</p> Signup and view all the answers

    The _______ chromosome is associated with facultative heterochromatin.

    <p>inactive X</p> Signup and view all the answers

    How does heterochromatin affect nearby genes?

    <p>It can affect the expression of nearby genes through position-effect variegation.</p> Signup and view all the answers

    Match the type of heterochromatin with its description:

    <p>Constitutive heterochromatin = Regions found throughout chromosomes and has structural functions. Facultative heterochromatin = Euchromatin that can convert based on developmental needs.</p> Signup and view all the answers

    Euchromatin is more densely packed than heterochromatin.

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

    What role does RNA-induced transcriptional silencing (RITS) play in heterochromatin?

    <p>It is responsible for the continuous turnover of transcribed DNA in heterochromatin.</p> Signup and view all the answers

    Study Notes

    Cell Cycle Checkpoints

    • Cell cycle checkpoints are control mechanisms in eukaryotic cell cycles
    • They ensure proper progression
    • Each checkpoint is a potential termination point assessing cell conditions
    • Progression to the next phase only occurs under favorable conditions
    • Key checkpoints: G1 (Start/restriction), G2/M, and metaphase-to-anaphase (spindle)
    • Progression determined by cyclin-dependent kinases (CDKs) activated by cyclins
    • Different cyclins produced at each cell cycle stage to control specific events

    Phases of Cell Cycle

    • A typical eukaryotic cell cycle (e.g., human cells in culture) lasts approximately 24 hours
    • Duration varies between organisms and cell types (e.g., yeast in 90 minutes)
    • Divided into interphase and mitotic (M) phase
    • Interphase: cell growth and chromosome copying
    • Mitotic phase: mitosis and cytokinesis

    Interphase

    • Consists of three phases: G1, S, and G2
    • G1 phase: Longest and most variable; cell gathers nutrients, synthesizes RNA and proteins needed for DNA replication
    • S phase: DNA synthesis; DNA contents are doubled, and new chromatids are formed (about 7.5-10 hours)
    • G2 phase: Cell growth and reorganization of cytoplasmic organelles; cell checks for DNA replication errors; cells prepare to enter the mitotic cycle

    Mitosis

    • Mitosis: process of chromosome segregation and nuclear division followed by cell division. Creating daughter cells with the same DNA content.
    • Stages Include:
      • Prophase: Chromatin condense, visible chromosomes form, nuclear envelope breaks down
      • Metaphase: Chromosomes align at the metaphase plate, spindle fibers attach to chromosomes
      • Anaphase: Sister chromatids separate and move to opposite poles
      • Telophase: Chromosomes decondense, nuclear envelope reforms, cytoplasm divides (cytokinesis)

    Cytokinesis

    • Cytokinesis: Cytoplasmic division that completes mitosis (formation of two daughter cells)

    Meiosis

    • Meiosis: Two sequential nuclear divisions to produce gametes (sex cells) with half the chromosome number and DNA content of somatic cells
    • Important for genetic diversity and reproduction
    • Meiosis differs in males and females: 1) Males- producing unique, haploid spermatids capable of differentiation into spermatozoa 2) Females- produces one haploid ovum and three haploid polar bodies
    • Stages: Meiosis I and Meiosis II (with prophase, metaphase, anaphase and telophase phases) reducing the DNA content from (4d) to (1d)

    Chromatin

    • Chromatin: Complex of DNA and proteins found in eukaryotic cells, packaging DNA into a compact form
    • Two types of chromatin: 1) Euchromatin: less compact, active transcription 2) Heterochromatin: more compact, less accessible for transcription
    • Nucleosomes: DNA wrapped around histone proteins, the fundamental subunit of chromatin
    • Importance in DNA packaging, regulation of gene expression, and maintaining chromosome integrity

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    Test your knowledge on the cell cycle, its checkpoints, and phases. This quiz covers key concepts such as G1, G2, and the role of cyclins and CDKs in controlling cell progression. Perfect for biology students looking to reinforce their understanding of eukaryotic cell cycles.

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