CELL CYCLE

CELL CYCLE

1. Cell division of germ cells

   • oogonia
   • spermatozoa
   • Diploid to Haploid

2. Meiosis I (Reductional Division)

   • Prophase I
     • Leptotene
       • Zygotene
         • Pachytene
           • Diplotene
             • Diakinesis
     • 1. Chromatin condenses
       • 2. Homologous maternal and paternal chromosomes pairs up
         • 3. The nucleolus and nuclear envelope disappear.
   • Metaphase I
     • 1. Homologous pairs of chromosomes align on the equatorial plate
       • 2. Spindle fibers from either pole attach to the kinetochore
   • Anaphase I
     • Chromosomes migrate to the poles.
   • Telophase I
     • 1. Each daughter cell now contains 23 chromosomes (n) number but has a 2CDNA content (the diploid amount)
       • 2. Each chromosome is composed of two similar sister chromatids

3. Meiosis II (Equatorial division)

   • Begins soon after the completion of meiosis I
     • Then, a brief interphase without DNA replication.
   • Prophase II
     • 1. Disintegration of nucleolus and nuclear envelope
       • 2. Movement of centrioles to opposite poles
         • 3. Spindle fibers develop at right angles to the spindle axis of meosis I.
   • Metaphase II
     • 1. Chromosomes arrange themselves at the equator
       • 2. Attachment of chromosomes to spindle fibre
   • Anaphase II
     • 1. Centromeres divide
       • 2. Chromatids are pulled to opposite poles
         • 3. Chromatids become the chromosomes of the daughter cells
   • Telophase II
     • 1. Chromosome uncoil and become indistinct
       • 2. Spindle disintegrates
         • 3. Nuclear envelope and nucleolus reform

4. PMAT

   • Prophase
     • Chromatin becomes visible in the nucleus
     • Centrioles move to opposite ends of the cell
   • Metaphase
     • Spindle Fibers surround the chromosome at the nucleus
   • Anaphase
     • The pair of chromosome go to the kinetochore and separate and move to opposite ends of the cell
   • Telophase
     • Chromatids move to opposite poles of the cell

5. Cytokinesis

   • The cell is split into two daughter cells each having one nucleus.

6. Interphase

   • Gap 1
     • Cell grow, develop, and gain ATP
   • S Phase
     • DNA is copied
   • Gap 2
     • Cell double checks the duplicated chromosomes for error and making any repairs

7. Mitosis

   • Cell Division
   • Cell divides into two daughter cells