CELL DIVISION

• Cell division types

  • Mitosis
  • Meiosis
• Eukaryotic cells have a specific number of chromosomes
• Cell cycle

  1. Interphase (G1, S, G2)

  2. Mitosis (Prophase, Metaphase, Anaphase, Telophase, Cytokinesis)
• Interphase


  Cell grows, replicates chromosomes, and prepares for cell division
• Interphase stages

  • Growth 1 (G1)
  • Synthesis (S)
  • Growth 2 (G2)
• G1


  Organelles double
• S


  DNA is replicated
• G2


  Proteins needed for mitosis are produced
• Mitosis

  1. Prophase

  2. Metaphase

  3. Anaphase

  4. Telophase

  5. Cytokinesis
• In some human cells, interphase lasts 15.3 hours, while mitosis lasts only 0.7 hours
• Chromosomes


  • Must DUPLICATE and SEPARATE during mitosis
• Chromatin


  Tightly packaged DNA
• Prophase


  1. Chromosomes become chromatids

  2. Centromere connects chromatids

  3. Spindle fibers begin to form

  4. Centrioles move to opposite sides

  5. Nuclear membrane breaks down
• Metaphase


  1. Centromeres of chromatid pairs line up in the middle

  2. Chromatids attach to spindle fibers
• Anaphase


  1. Spindle fibers pull chromatids apart

  2. Chromatids move to opposite sides
• Telophase


  1. Spindle fibers break up

  2. Nuclear membrane reforms

  3. Furrow begins to develop
• Cytokinesis


  Two identical cells completely divide
• Meiosis


  Type of cell division in sexually reproducing organisms that reduces the number of chromosomes in gametes
• Diploid (2n)


  Cell with two of each kind of chromosome
• Haploid (n)


  Cell with one of each kind of chromosome

  
• Homologous chromosomes


  Paired chromosomes with genes for the same trait arranged in the same order
• Allele


  Gene form for each variation of a trait of an organism
• Genetics is the study of how traits are passed from parents to offspring
• DNA is the molecule that holds the genetic information for a cell and organism
• Gene


  Specific segment of a DNA molecule that holds the information for one specific protein
• Genes are the basic unit of heredity
• Inheritance


  Passing of traits from parents to offspring, occurs in both sexual and asexual reproduction
• CELL CYCLE

  • is a series of events that takes place in a cell as it grows and divides.
• a cell SPENDS MOST OF ITS TIME in interphase
• during interphase, the cell grows, replicates its chromosomes, and prepares for cell division.
• after the interphase, the cell undergoes mitosis and completes its division
• Interphase - is when the CELL GROWS, and the organelles DOUBLE prior to the actual splitting of the nucleus
• 93% of a cell's life is spent in interphase
• each cell needs a complete and identical set of DNA
• Mitosis - the process by which the cell nucleus DIVIDES INTO TWO IDENTICAL cell nuclei
• Spindle fiber - a fibrous structure from the cytoplasm which forms to the centriole
• Metaphase plate - the location where the centromeres LINE UP in the center of the cell
• Haploid cells are called gametes
• Gametes are either sperm or eggs
• humans have 23 pairs of chromosomes