CELL DIVISION

• Cell Division - Biological Basis of life. Reproduction: to produce new individual of the same kind

  • Maintains the genome: Keeps the genomic information consistent between generations

  • Cell Multiplication: Increase in the number of cells for growth, development and repair
• Types of Cells

  Somatic - Make up all the body tissues and organs. Diploid Chromosomes. Undergo Mitosis

  Germinal -Gametes: Reproductive cells. Haploid Chromosomes. Undergo Meiosis
• CHROMOSOME

  A) Sister Chromatids

  B) Centrocomere

  
• Haploid Chromosomes - One copy of genetic material subdivided into chromosomes
• Diploid Chromosomes - Two copies of genetic material subdivided into chromosomes
• Homologous Chromosome - Have alleles for same genes at specific loci

  • Similar but NOT identical
• Sister Chromatids - Have the same alleles for each gene

  • Identical chromosomes
• Prophase - chromosomes are duplicated. Centrosomes begin moving apart; Nuclear envelope is fragmenting and nucleolus will disappear.
• Metaphase - Chromosomes (consists of 2 sister chromatids) are at metaphase plate (center/fully form spindle)
• Anaphase - daughter chromosomes (consists of one chromatid) are moving toward the poles of spindle.
• Telophase - Daughter cell are forming as nuclear envelopes and nucleoli appear. Chromosome will become indistinct chromatin.
• Meiosis I: Prophase I consists of leptotene, zygotene, pachytene, diplotene, diakinesis
• Meiosis I: Prophase I: Leptotene

  • Condensation of chromosomes

  • Shortening and thickening of chromosomes

  • Doubled chromosomes
• Meiosis I: Prophase I: Zygotene

  • Pairing of homologous chromosomes
  • Synapsis begins
• Meiosis I: Prophase I: Pachytene

  • Bivalent formed

  • Crossing-over occurred
• Meiosis I: Prophase I: Diplotene

  • Coiling stage

  • Chiasmata holds the homologous chromosomes
• Meiosis I: Prophase I: Diakinesis

  • Recondensation

  • Tetrad chromosomes are visible

  • Terminalization: chiasmata at the ends

  • End of Prophase I

  • Nucleolus vanishes

  • Nuclear membrane breaks down
• Meiosis I: Metaphase I

  • Chromosomes are :Attached to the meiotic spindle

  • Arranged at the metaphase plate
• Meiosis I: Anaphase I

  • Separation of homologous chromosome, each moving to opposite poles

  • Sister chromosomes remain attached
• Meiosis I: Telophase I

  • Homologous chromosomes reached the poles

  • Nuclear envelopes form

  • Cytokinesis follows
• Meiosis II: Prophase II

  • Nuclear envelope breaks down

  • Spindle apparatus forms
• Meiosis II: Prophase II

  • Nuclear envelope breaks down

  • Spindle apparatus forms
• Meiosis II: Anaphase II

  • Centromeres separate

  • Sister chromatids are now individual chromosomes

  • Chromosomes move toward the poles
• Meiosis II: Telophase II

  • Nuclear envelope forms around each set of chromosomes

  • Cytokinesis occurs

  • Formation of 4 daughter cells, each with haploid set of chromosomes
• DIFFERENCE OF MITOSIS AND MEIOSIS

  A) Mitosis

  B) Meiosis