Cell Division and Cell Cycle Quiz

Cell Division and Cell Cycle

• Cell division is a vital part of the cell cycle.
• It results in genetically identical daughter cells.
• Cells duplicate their genetic material before division, ensuring each daughter cell receives an exact copy of DNA.

Functions of Cell Division

• Reproduction: Single-celled eukaryotes like amoebas divide to create new organisms.
• Growth and development: The fertilized egg cell divides to form new cells, enabling growth and development.
• Tissue renewal: Dividing bone marrow cells generate new blood cells, constantly renewing tissues.

DNA

• DNA is the genetic information (genome).
• DNA is organized into chromosomes.

Phases of the Cell Cycle

• Interphase: The normal cell activity stage, consisting of three sub-phases.
  • G1 (Gap 1): Primary growth phase.
  • S (Synthesis): DNA replication phase.
  • G2 (Gap 2): Secondary growth phase.
• Mitotic phase: Cell division phase, with further sub-phases.
  • Mitosis: Process of nuclear division. (further sub-phases Prophase, Metaphase, Anaphase, and Telophase)
  • Cytokinesis: The division of the cytoplasm.
• Different cell types divide at different rates. Some cells rarely or never divide.

Mitosis and Meiosis

• Normal cells contain 46 chromosomes (diploid).
• Mitosis produces genetically identical daughter cells, also with 46 chromosomes, occurring in most cells.
• Meiosis produces haploid gametes (sperm and egg cells), containing only one set of chromosomes (23 in humans) for sexual reproduction.

Two Fundamental Cell Types

• Prokaryotic: Bacteria and other prokaryotic cells multiply by binary fission.
• Eukaryotic: Cells with a nucleus, follow the elaborate cell cycle of phases described in the information above.

Packing for the Move...

• Protein complexes (condensins) compact chromosomes for DNA duplication and division.

Structure of a Eukaryotic Chromosome

• A chromosome is composed of two sister chromatids, joined by a centromere.

Metaphase Chromosome

• The centromere, a constricted region, contains two kinetochores (protein discs).
• Kinetochores are points of attachment for microtubules, crucial in chromosome movement during cell division.

Eukaryotic Cell Cycle

• The eukaryotic cell cycle has two major phases.
  • Interphase (G1, S, G2)
  • Mitotic (M) phase, consisting of mitosis (and cytokinesis) which both involve a number of events
• DNA is uncondensed (chromatin) during interphase, condensed (chromosomes) during the mitotic phase

Mitosis Steps (Simplified)

• Prophase: Chromosomes condense.
• Metaphase: Chromosomes align.
• Anaphase: Sister chromatids separate.
• Telophase and cytokinesis: Nuclear envelopes reform; the cytoplasm divides.

Mitotic Division of an Animal Cell

• Visual representation of the dynamic events of mitosis.

G2 of Interphase

• Two centrosomes form from replication of a single centrosome.
• Each contains centrioles in animal cells.
• Chromosomes, duplicated in S phase, appear uncondensed (in a granular form).

Prophase

• Chromatin fibers condense into chromosomes.
• Nucleoli disappear.
• Two identical sister chromatids join.
• Mitotic spindle begins to form.
• Asters ("stars") emerge from centrosomes.
• Centrosomes move apart via elongation of microtubules.

Metaphase

• Chromosomes align on the metaphase plate. An imaginary plane that splits the cell.
• Kinetochores (on sister chromatids) attach to kinetochore microtubules.
• Spindle microtubules form from opposite poles.

Telophase

• Two daughter nuclei form.
• Nuclear envelopes form around the nuclei.
• Chromosomes decondense.
• Less condensed chromosomes.
• Mitosis, the division of one nucleus into two genetically identical nuclei is complete.

Cells Divide at Different Rates

• Cell division rates vary depending on the specific cell type and its function.
  • Skin cells divide quickly.
  • Red blood cells have a short lifespan.
  • Other cells have much longer lifespans.

Abnormalities of Cell Division

• Defects in cell division/cell cycle can originate by chromosomal disruptions.
• Major chromosomal abnormalities normally result in spontaneous embryonic loss.
• Chromosomal disorders can arise from issues in number/placement of chromosomes.
• Cells can have extra chromosomes during division (or none), as a result.
• Abnormal chromosome numbers/structures are usually incompatible with life.
• Abnormalities can cause diseases like cancer, arising from uncontrollable cell proliferation.

Regulation of the Cell Cycle

• Control mechanisms direct the ordered events of the cell cycle.
• The cell cycle contains built-in checkpoints.
• External and internal factors influence control.

Cell Cycle Checkpoints

• Checks for proper cell size and DNA integrity.
• Ensures DNA is correctly replicated.
• Verifies correct chromosome alignment/attachment during mitosis.

Cyclin-dependent Kinases (CDKs)

• CDKs are protein kinases that drive the cell cycle by activating or deactivating other proteins.
• They require cyclins to become activated.

Cyclin Dependent Kinase Inhibitors (CKIs)

• Regulators that inhibit/control CDKs.

External Factors

• Growth factors influence cell division.
• Platelet-derived growth factor (PDGF) stimulates cells to divide.
• Cell signaling mechanisms control which cell types divide, how fast, and when.

Role of p53 in Cell Cycle Control

• The p53 protein is vital and has an essential role in controlling the cell cycle when DNA is damaged.
• p53 is a transcription factor that responds to DNA damage.
• If DNA is damaged, p53 promotes cell cycle arrest and triggers apoptosis.

Tumor Suppressor Genes

• Tumor suppressor genes normally slow cell division or induce programmed cell death (apoptosis).
• Mutations in these genes can lead to uncontrolled cell growth.

Cancer

• Cancer cells evade normal mechanisms and controls, leading to uncontrolled division and invasion of other tissues.
• Cancer cells can manufacture their own growth factors, have signaling pathway problems, or issues with their cell cycle control system.
• Cancer cells may stop dividing at random, not at the normal checkpoints.

Additional Information (Checkpoints/Mechanism)

• Specific molecular mechanisms and proteins are involved in cell cycle checkpoints to ensure accurate cell division.

Test your knowledge on the processes of cell division and the cell cycle. This quiz covers vital concepts including DNA organization, phases of the cell cycle, and functions of cell division in growth, reproduction, and tissue renewal. Perfect for students studying biology.