Topic 5) The Mitotic Cell Cycle (AS)

🧬 Topic 5: The Mitotic Cell Cycle

5.1 Replication and Division of Nuclei and Cells

• Purpose of Mitosis

  • Ensures the production of two genetically identical daughter cells.

  • Crucial for growth, tissue repair, and asexual reproduction.

• Phases of the Cell Cycle

  • Interphase: Preparation phase consisting of G₁ (cell growth), S (DNA replication), and G₂ (final preparations for division).

  • M Phase (Mitotic Phase): Includes mitosis (nuclear division) and cytokinesis (cytoplasmic division).

• Stages of Mitosis

  • Prophase: Chromosomes condense and become visible; nuclear envelope begins to break down.

  • Metaphase: Chromosomes align along the metaphase plate; spindle fibers attach to centromeres.

  • Anaphase: Sister chromatids separate and move toward opposite poles.

  • Telophase: Nuclear envelopes reform around each set of chromosomes; chromosomes decondense.

  • Cytokinesis: Division of the cytoplasm, resulting in two daughter cells.Study Rocket+4Wikipedia+4TutorChase+4Wikipedia+3TutorChase+3TutorChase+3Wikipedia+5Study Rocket+5TutorChase+5

• Significance of Mitosis

  • Maintains genetic consistency across cell generations.

  • Facilitates tissue growth and repair.

  • Enables asexual reproduction in certain organisms.A Level Biology+4PropG+4Khan Academy+4Save My Exams

5.2 Chromosome Behavior in Mitosis

• Chromosome Structure

  • Each chromosome consists of two identical sister chromatids joined at the centromere.

  • Chromatids are held together by cohesin proteins until anaphase.TutorChase+1Wikipedia+1TutorChase+2Wikipedia+2Wikipedia+2

• Spindle Apparatus

  • Composed of microtubules emanating from centrosomes.

  • Spindle fibers attach to the kinetochore regions of chromosomes.TutorChase+3Study Rocket+3TutorChase+3

• Anaphase Mechanism

  • Cohesin proteins are cleaved by separase, allowing sister chromatids to separate.

  • Motor proteins like dynein and kinesin facilitate the movement of chromatids toward opposite poles.Wikipedia+2TutorChase+2Wikipedia+2

• Consequences of Errors

  • Nondisjunction can lead to aneuploidy, resulting in cells with an abnormal number of chromosomes.

  • Such errors can contribute to genetic disorders and cancer development.