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Lecture 8a-for Exam 3-Mitosis & Cell Cycle

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  • What is the primary purpose of cell division?
    Cell division is essential for reproduction, growth, embryonic development, renewal, and repair in living organisms.
  • What is a genome?
    The genome is all the DNA in a cell, which can be a single DNA molecule in prokaryotes or multiple molecules in eukaryotes.
  • What is chromatin?
    Chromatin is a complex of DNA and protein that condenses to form chromosomes during cell division.
  • Define sister chromatids.
    Sister chromatids are identical copies of a chromosome, joined at the centromere before cell division.
  • What are the two main processes of eukaryotic cell division?
    Mitosis divides the genetic material in the nucleus, and cytokinesis divides the cytoplasm.
  • What is the mitotic spindle and its function?
    The mitotic spindle is made of microtubules that control chromosome movement during mitosis.
  • What happens during metaphase of mitosis?
    Chromosomes line up at the metaphase plate, an imaginary plane midway between the spindle's two poles.
  • How do sister chromatids separate during anaphase?
    Cohesins are cleaved by separase, allowing sister chromatids to move along kinetochore microtubules to opposite poles.
  • How does cytokinesis differ in animal and plant cells?
    In animal cells, a cleavage furrow forms; in plant cells, a cell plate forms to divide the cells.
  • What is binary fission?
    Binary fission is prokaryotic cell division where the chromosome replicates and the cell splits into two daughter cells.
  • What are the phases of mitosis?
    Prophase, prometaphase, metaphase, anaphase, and telophase.
  • What is the role of cyclins and CDKs in cell cycle control?
    Cyclins bind to cyclin-dependent kinases (CDKs) to activate them, regulating progression through the cell cycle.
  • What is MPF and its function?
    Maturation-promoting factor (MPF) is a cyclin-CDK complex that triggers the cell's passage from G2 phase into mitosis.
  • What happens at the G1 checkpoint?
    The cell decides whether to divide, enter G0 (non-dividing state), or continue the cycle based on internal and external signals.
  • How do cancer cells differ in cell cycle regulation?
    Cancer cells can divide without normal growth signals, may produce their own growth factors, or have abnormal cell cycle control.
  • What is meiosis and its purpose?
    Meiosis is a type of cell division producing four genetically distinct haploid gametes for sexual reproduction.
  • What are homologous chromosomes?
    Pairs of chromosomes, one from each parent, that have the same length, centromere position, and genes controlling the same traits.
  • What occurs during prophase I of meiosis?
    Homologous chromosomes pair and crossing over occurs at chiasmata, exchanging genetic material.
  • How does meiosis I differ from meiosis II?
    Meiosis I separates homologous chromosomes; meiosis II separates sister chromatids.
  • What are three mechanisms that contribute to genetic variation?
    Independent assortment of chromosomes, crossing over, and random fertilization.
  • What is independent assortment?
    Random orientation of homologous chromosome pairs at metaphase I, producing 2^n possible chromosome combinations.
  • What is crossing over?
    Exchange of genetic material between homologous chromosomes during prophase I, creating recombinant chromosomes.
  • Why is random fertilization important?
    Any sperm can fuse with any egg, increasing genetic variation in offspring.
  • What is the evolutionary significance of genetic variation?
    Genetic variation provides material for natural selection, enabling populations to adapt to changing environments.