Mitosis

• What is the cell cycle?

  The cell cycle describes the events that take place as one parent cell divides to produce two new daughter cells.
• What happens during mitosis (M-phase)?

  A nucleus divides by mitosis, followed by cytokinesis, producing two daughter cells.
• What is interphase?

  Interphase is the period between divisions when DNA is replicated and the cell prepares for division.
• What phases is interphase divided into?

  Interphase is divided into G1, S, and G2 phases.
• What occurs during the G1 phase of interphase?

  Synthesis of new organelles and proteins, an increase in cell volume, lasting approximately 10 hours.
• What happens during the S phase of interphase?

  DNA is replicated during the S phase, which lasts about 9 hours.
• What happens during the G2 phase of interphase?

  The volume of the cell increases, and proteins needed for mitosis are synthesized, lasting around 4 hours.
• What is checked at the G1/S checkpoint?

  The cell checks that the chemicals needed for DNA replication are present and that the DNA is undamaged before entering S-phase.
• What are cell cycle checkpoints?

  Checkpoints are regulatory mechanisms that ensure the cell cycle progresses correctly.
• What is checked at the G2/M checkpoint?

  The cell ensures DNA has been replicated without errors before entering mitosis.
• What are the stages of interphase and their durations?

  • G1: Synthesis of new organelles and proteins, 10 hours.
  • S: DNA replication, 9 hours.
  • G2: Increase in cell volume, synthesis of mitotic proteins, 4 hours.
• What are the roles of cell cycle checkpoints?

  • Prevent uncontrolled division (reducing tumour risk).
  • Detect and repair DNA damage.
  • Ensure DNA is replicated only once per cycle.
• What happens during the M phase of the cell cycle?

  • Nuclear division occurs in four stages: prophase, metaphase, anaphase, telophase.
  • Cytokinesis follows, dividing the cytoplasm.
• What occurs during the S phase of interphase?

  • DNA is replicated.
  • Housekeeping genes are copied first.
• What are the key processes in the G1 phase of interphase?

  • Cells grow and increase in volume.
  • Protein synthesis occurs.
  • Organelles are replicated.
  • The G1 checkpoint ensures DNA is undamaged.
• What happens during the G2 phase of interphase?

  • Cells continue to grow and increase in volume.
  • The G2/M checkpoint ensures DNA has been replicated without errors.
• What is the role of the metaphase checkpoint?

  The metaphase checkpoint ensures that the cell is ready to complete mitosis.
• How does the p53 gene influence the cell cycle?

  The p53 gene helps regulate the G1 phase to ensure proper cell cycle progression.
• What are housekeeping genes, and when are they copied?

  Housekeeping genes are copied first during the S-phase.
• What is unique about the genetic information in cells produced by mitosis?

  All daughter cells contain the same genetic information as the original parent cell.
• What is mitosis used for in the body?

  Mitosis is used for growth and tissue repair.
• In which organisms is mitosis used for asexual reproduction?

  Mitosis is used in single-celled protists, yeast, and some plants.
• How does mitosis contribute to cell specialization?

  Only some genes are "switched on" to make cells specialize.
• How do all complex organisms originate and develop?

  All complex organisms originate from a single fertilized egg through mitosis.
• What is the outcome of mitosis in terms of daughter cells?

  Mitosis produces two daughter cells, genetically identical to the parent cell.
• How do chromosomes behave during mitosis?

  Chromosomes are copied and divided between the two daughter cells.
• What method do bacteria use to replicate?

  Bacteria replicate by binary fission, not mitosis.
• What are homologous chromosomes?

  Homologous chromosomes are pairs holding the same genes from each parent.
• What is a histone?

  A histone is a protein that DNA wraps around to form chromatin.
• How many chromosomes and homologous chromosome pairs do most human body cells contain?

  Most human body cells contain 46 chromosomes and 23 pairs of homologous chromosomes.
• What is the centromere of a chromosome?

  The centromere is where two sister chromatids are joined together.
• What are chromatids?

  Chromatids are the “arms” of a replicated chromosome.
• What happens to chromatin during cell division?

  Chromatin coils up to form visible chromosomes.
• How thick are chromatin threads and chromosomes?

  • Chromatin thread: 30 nm thick.
  • Chromosome: 500 nm thick.
• What is the purpose of supercoiling during cell division?

  Supercoiling makes genetic material short and sturdy for movement.
• What happens during prophase, the longest stage of mitosis?

  • Chromosomes condense to form sister chromatids.
  • The nuclear envelope breaks down.
  • The centriole divides and moves to opposite poles.
• What occurs during metaphase, a short stage of mitosis?

  • Chromosomes move to the equator of the cell.
  • Chromosomes attach to spindle fibres by their centromeres.
• What are the main events of anaphase?

  • The centromere splits.
  • Spindle fibres shorten, pulling sister chromatids apart.
• What happens during telophase in mitosis?

  • Chromatids reach the poles.
  • New nuclear envelopes form around each set.
• What is cytokinesis, and when does it occur?

  Cytokinesis is the division of the cytoplasm after mitosis.