Cell Division

• What is genetic information copied and passed on to?

  Daughter cells
• What are chromosomes made of?

  DNA, proteins, and RNA
• When do chromosomes become visible?

  At the onset of cell division
• What happens to each DNA molecule before cell division?

  It makes a copy of itself
• What are the two identical threads of DNA called?

  Chromatids
• Where are chromatids joined?

  At the centromere
• How many chromosomes do humans have?

  46 chromosomes
• What are homologous pairs?

  Matching pairs of chromosomes

  
• What is the diploid number in humans?

  46 chromosomes
• What is the haploid number in human gametes?

  23 chromosomes
• What does mitosis produce?

  Two genetically identical daughter cells
• What is the cell cycle?

  A regular pattern of events in dividing cells
• What occurs during interphase?

  Replication of DNA and organelles
• What are the four stages of mitosis?

  • Prophase
  • Metaphase
  • Anaphase
  • Telophase

  
• What is synthesized during interphase?

  Ribosomal material, ATP, and proteins
• What is the longest part of the cell cycle?

  Interphase

  
• Where does mitosis occur in plants?

  In the meristems
• What happens to DNA during prophase?

  It condenses into chromosomes
• What forms from each centriole during prophase?

  Protein microtubules
• What happens to the nuclear membrane during prophase?

  It disintegrates
• What occurs during metaphase?

  Chromosomes align at the spindle's equator

  
• What happens during anaphase?

  Chromatids are pulled to opposite poles

  
• What occurs during telophase?

  Chromatids uncoil and the nuclear membrane reforms
• How does cytokinesis occur in animal cells?

  By constriction from outside inwards
• How does cytokinesis occur in plant cells?

  A cell plate forms across the equator
• What happens to the number of chromosomes during the cell cycle?

  It remains constant
• What happens to DNA content during the S phase?

  It increases from 20 to 40

  
• What is the significance of mitosis?

  It is essential for growth and repair
• What is a tumor?

  An irregular mass of cells
• What initiates cancers?

  Mutations in genes controlling division
• What does meiosis produce?

  Gametes with half the chromosome number
• What is the role of interphase in meiosis?

  It is essential for DNA replication
• What happens during prophase I of meiosis?

  Homologous chromosomes associate as bivalents

  
• What is crossing over?

  Swapping of chromosome pieces at chiasmata

  
• What occurs during metaphase I?

  Homologous chromosomes arrange randomly on the equator
• What happens during anaphase I?

  Chromosomes in bivalents separate to opposite poles
• What happens during telophase I?

  The nuclear envelope reforms around haploid chromosomes
• What is the result of meiosis II?

  Four genetically different haploid daughter cells
• Compare mitosis and meiosis.

  Mitosis:

  • One division, 2 identical daughter cells
  • Chromosome number unchanged
  • No crossing over

  
  

  Meiosis:

  • Two divisions, 4 genetically different cells
  • Chromosome number halved
  • Crossing over occurs

  
• What introduces genetic variation in meiosis?

  Crossing over and independent assortment