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Cell Cycle and Mitosis - General Biology

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  • What is the primary role of cell division in unicellular organisms?
    Reproduction of the entire organism by division of one cell.
  • What is the cell cycle?
    The life of a cell from its formation to its own division, including growth and DNA replication.
  • What is the difference between somatic cells and gametes in terms of chromosome number?
    Somatic cells are diploid (2n) with two sets of chromosomes; gametes are haploid (n) with half the chromosome number.
  • What is chromatin?
    A complex of DNA and protein in eukaryotic cells that condenses to form chromosomes during cell division.
  • What are nucleosomes?
    DNA wrapped around histone proteins, compacting DNA and regulating gene expression.
  • What are sister chromatids?
    Identical copies of a chromosome joined at the centromere after DNA replication.
  • What is the centromere?
    The region where sister chromatids are most closely attached.
  • What are the main phases of the cell cycle?
    Interphase (G1, S, G2) for growth and DNA replication, and M phase for mitosis and cytokinesis.
  • What happens during the G1 phase?
    Cell growth before DNA replication.
  • What occurs in the S phase of the cell cycle?
    DNA replication and duplication of chromosomal proteins.
  • What is the function of the mitotic spindle?
    Composed of microtubules, it controls chromosome movement during mitosis.
  • What are kinetochores?
    Protein structures at the centromere where spindle microtubules attach.
  • What is the spindle checkpoint (SAC)?
    A control point ensuring all chromosomes are properly attached to spindle fibers and aligned.
  • What enzyme cleaves cohesin to separate sister chromatids during anaphase?
    Separase cleaves cohesin, allowing chromatids to separate.
  • What occurs during telophase?
    Chromosomes decondense, nuclear envelopes reform, and nucleoli reappear.
  • How does cytokinesis differ between animal and plant cells?
    Animal cells form a cleavage furrow; plant cells form a cell plate.
  • What are cyclins and Cdks?
    Cyclins are proteins whose levels fluctuate; Cdks are enzymes that phosphorylate proteins to drive cell cycle progression.
  • What is MPF?
    Maturation-promoting factor, a cyclin-Cdk complex that triggers mitosis.
  • What is density-dependent inhibition?
    A process where crowded cells stop dividing to prevent overgrowth.
  • What characterizes cancer cells in terms of cell cycle control?
    They lose normal control, may produce their own growth factors, and can divide indefinitely.