chapter 1

• Binary fission


  A type of reproduction in which the cell grows to double its size and then divides into 2 identical cells
• Prokaryotes

  • Reproduce using Binary fission
• Binary fission in prokaryotes


  1. The single circular chromosome begins to replicate at the origin of replication

  2. As the chromosome replicates the cell elongates

  3. Once the replication is complete and the cell is twice the size, proteins cause the plasma membrane to pinch inwards

  4. Dividing the parent cell into 2 identical daughter cells
• Eukaryotic cell cycle


  Consists of interphase (G1, S, and G2 phases) followed by mitosis, and cytokinesis, for cell division
• Eukaryotic cell cycle


  Allows cells to grow, replicate their DNA, and divide into two daughter cells for reproduction or tissue renewal
• G1 phase


  The cell decides if it will split or not, once it passes this checkpoint it moves into the S phase and is committed to dividing
• G1 checkpoint


  1. The cell examines if the internal and external environment of the cell are right for division

  2. The cell looks at: growth factors, cell size, nutrients, DNA damage
• G2 phase


  Before the cell goes into mitosis, the cell completes some final checks: to determine if DNA is damaged, to determine if DNA replication has happened correctly, proteins have been synthesised that are required for mitosis, cell size is large enough
• If there is damage or DNA replication has not been completed correctly


  The cycle will pause at this point and try to repair the damage or let DNA replication finish
• If the DNA can not be repaired

  The cell will undergo apoptosis to prevent damage being passed onto daughter cells
• M phase


  The M checkpoint also known as the spindle checkpoint as the cell checks whether the sister chromatids are correctly attached to the spindle microtubules
• Prophase


  Chromatin condenses into visible chromosomes, nuclear envelope breaks down, spindle fibbers form
• Metaphase


  Chromosomes align at the metaphase plate, spindle fibbers attach to centromeres
• Anaphase


  Sister chromatids separate and move towards opposite poles of the cell
• Telophase


  Chromatids reach the poles, nuclear envelopes re-form around the separated chromosomes, and spindle fibbers disassemble
• Cytokinesis


  The final stage of the cell division process in which the cytoplasm of the parent cell divides, resulting in the formation of two daughter cells
• Apoptosis


  Programmed cell death, characterized by controlled cellular dismantling and fragmentation, often serving regulatory functions in development, homeostasis, and immunity
• Apoptosis can be triggered by


  Various factors including developmental signals, cellular damage, DNA mutations, and stress responses within the organism
• Disruption to the regulation of the cell cycle, such as mutations in key regulatory genes, can lead to uncontrolled cell division or apoptosis
• Stem cells


  Unspecialised cells which are able to divide and differentiate into other cell types
• Stem cells


  • Undifferentiated cells capable of self-renewal and differentiation into various specialized cell types, playing crucial roles in development and regeneration