Cell Cycle Overview Quiz

Cell Cycle

• The cell cycle is a series of events that lead to cell maturity and division.
• The core stages are interphase, where the cell lives or prepares for division, and mitosis (M phase), where the cell divides itself.
• Most cells in a multicellular organism are in interphase.

Interphase

• Interphase is a period of growth and preparation for division. It is composed of G1, S, and G2 phases.
• G1 Phase (Gap 1): The cell grows, accumulates energy, and produces proteins needed for DNA replication. This phase marks a checkpoint to determine if the cell is ready to proceed to DNA replication.
• S Phase (Synthesis): DNA replication takes place, resulting in two identical copies of each chromosome, called sister chromatids. The centrosomes also duplicate here, preparing for mitosis.
• G2 Phase (Gap 2): The cell replenishes energy stores, synthesizes proteins needed for chromosome manipulation, and duplicates some organelles. Cells also ensure the proper completion of DNA replication prior to mitosis.
• G0 Phase (Resting Phase): Cells in this phase are not actively preparing to divide. They may re-enter the cell cycle when signaled. Cells that rarely divide usually remain in G0 permanently.

S Phase: DNA Replication

• DNA replication is crucial to ensure each daughter cell receives an accurate copy of the parent cell's genetic information.
• This process is based on complementary base pairing: adenine pairs with thymine, and cytosine pairs with guanine.

Cell Cycle Checkpoints

• There are internal mechanisms at checkpoints to prevent compromised cells from dividing.
• These operate near the end of G1, at the G2–M transition, and during metaphase.
• Checkpoints ensure conditions are favorable before proceeding.

Mitosis: Stages

• Prophase: The chromatin condenses into visible chromosomes, the nucleolus fades, the nuclear envelope disintegrates, and the mitotic spindle forms.
• Prometaphase: The nuclear envelope breaks down completely, spindle microtubules interact with chromosomes, and microtubules move chromosomes towards the center of the cell.
• Metaphase: Chromosomes align along the metaphase plate, each sister chromatid attaching to microtubules from opposite poles. This ensures each new cell receives one copy of each chromosome.
• Anaphase: Sister chromatids separate and are pulled toward opposite poles of the cell.
• Telophase: The chromosomes decondense back into chromatin, nuclear envelopes re-form around each set of chromosomes, and the spindle apparatus disassembles.

Cytokinesis

• Cytokinesis follows telophase and involves the division of the cytoplasm.
• In animal cells, a cleavage furrow forms, pinching the cell in two.
• In plant cells, a cell plate forms, creating two separate cell walls.

Functions & Importance of Mitosis

• Growth and Development: Mitosis supports the growth of multicellular organisms from a fertilized egg.
• Tissue Repair and Regeneration: Mitosis replaces lost or damaged cells in tissues.
• Asexual Reproduction: In some organisms, mitosis serves as a form of asexual reproduction, creating clones of the original organism.
• Developmental Plasticity and Cell Differentiation: Mitosis enables a single fertilized egg to become a complex organism with diverse cell types.
• Immune System Function: Mitosis is essential for the proliferation of lymphocytes, vital to the immune response.
• Maintenance of Chromosome Number: Mitosis ensures each daughter cell receives a complete copy of the parent cell's genetic material.
• Genetic Consistency: Mitosis guarantees that all body cells (except gametes) contain the same DNA.
• Cancer Prevention: Uncontrolled cell division can lead to cancer. Understanding mitosis is crucial for developing cancer treatments and prevention strategies.

Mitosis in Plant and Animal Cells

• Both follow the same basic process with some differences:
  • Centrosomes and Spindle Formation: Animal cells have centrosomes with centrioles, which are the organizing centers for spindle formation. Plant cells lack centrioles.

Test your knowledge on the stages of the cell cycle, including interphase and mitosis. This quiz assesses your understanding of the processes involved in cell growth, DNA replication, and division. Explore the key phases: G1, S, and G2, and their significance in cellular development.