The Cell Cycle Overview

The Cell Cycle

• The cell cycle is the life of a eukaryotic cell, describing how cells grow, create copies and divide.
• It is crucial for all somatic (body) cells to ensure identical DNA in each cell. Reproductive cells follow a different pathway.
• Parent cells are diploid and create two diploid daughter cells with their own distinct nuclei.
• Diploid means a pair of each chromosome (2n). Example: Humans have 23 pairs, totaling 46 chromosomes.
• The cell cycle has key phases: Interphase, Prophase, Metaphase, Anaphase, Telophase and Cytokinesis (IPMATC).
• Interphase is the largest portion of the cycle (95% growth).
• During Interphase, the cell grows, duplicates its DNA, and prepares for division. DNA copying is called synthesis or replication.
• Interphase has three key stages: G1, S, and G2.
• G1: Cell grows in size and develops, differentiation occurs.
• S: DNA synthesizes, creating two identical copies of all chromosomes/DNA. The DNA double helix is unzipped by helicase, nucleotides are added to both sides, and the process is completed with DNA polymerase.
• G2: Cell prepares for division and checks for errors.
• Mitosis follows Interphase (the splitting of the cell and its contents).
• Mitosis has four phases: Prophase, Metaphase, Anaphase, Telophase.
• Cytokinesis is the final stage, dividing the parent cell into two identical daughter cells.

Chromosome Structure

• A chromosome is a thread-like structure carrying genetic information.
• Chromosomes have a structure of two identical chromatids joined by a centromere.
• Chromatids are the identical halves of a replicated chromosome.

Importance in Organisms

• In unicellular organisms, the cell cycle is how they create new offspring.
• In multicellular organisms, the cell cycle is crucial for growth, specialization, and tissue formation (morphogenesis).
• Through cellular division, growth and differentiation take place. Different cells are assigned different jobs from specialized genes.

Disruptions in the Cell Cycle

• If genes or enzymes trigger the cell cycle too rapidly, uncontrolled cell division can occur, leading to cancer.

Stages of Mitosis

• Prophase: Chromosomes become visible as two chromatids, the nuclear envelope breaks down, centrioles become visible and present spindle fibers.
• Metaphase: Chromosomes align in the middle of the cell, the nuclear envelope is gone, spindle fibers reach the chromosomes.
• Anaphase: Spindle fibers pull sister chromatids to opposite poles of the cell. Chromosomes are split, sister chromatids are now their own chromosomes.
• Telophase: The nuclear envelope reforms around each set of chromosomes, chromosomes uncoil, spindle fibers disassemble, cleavage furrow starts forming.

This quiz covers the essential phases of the cell cycle, including Interphase, Mitosis phases (Prophase, Metaphase, Anaphase, Telophase), and Cytokinesis. Understand the importance of each stage for eukaryotic cells and learn how cells ensure each daughter cell has identical DNA. Test your knowledge on key definitions and functions within the cell cycle.