Cell Cycle

• Cell


  The basic unit of life in all living things
• Cell Theory


  • All organisms are made of cells

  The cell is the basic unit of life in all living things

  All cells come from pre-existing cells
• Two Types of Cells

  • Prokaryotic Cells

  Eukaryotic Cells
• Prokaryotic Cells


  Have no membrane covered nucleus

  Have no membrane-covered organelles

  Have circular DNA

  Are bacteria
• Eukaryotic Cells


  Have a nucleus

  Have membrane-covered organelles

  Have linear DNA

  Are all other cells
• Reproduction


  The biological process by which new individual organisms - "offspring" - are produced from their "parent" or parents
• Cell Division


  The process by which a parent cell divides into two or more daughter cells
• 2 types of Cell Division

  • Mitosis - Body cells

  Meiosis - Sex cells
• Somatic Cells


  Body cells, produced through mitosis, has 46 chromosomes (23 pairs)
• Homologous Chromosomes


  Each member of a chromosome pair
• Diploid (2n)


  Total of 46 chromosomes in people - zygote & somatic cells
• Haploid (n)


  Total of 23 chromosomes in people, gametes (sperm (X,Y) & egg (X,X))
• Chromosomes


  • Genetic information is passed from one generation to the next on chromosomes

  Before cell division, each chromosome is duplicated, or copied
• Sister Chromatids


  Each chromosome consists of two identical "sister" chromatids

  Each pair of chromatids is attached at an area called the centromere
• Cell Cycle


  The sequence of growth and division of a cell

  95% of cell cycle in interphase

  5% of cell cycle in mitosis
• Events of the Cell Cycle

  • Growth Stage 1 (G1)

  Synthesis Stage (S)

  Growth Stage 2 (G2)

  M Phase
• G1 Phase


  Cell increases in size, synthesizes new proteins and organelles
• S Phase

  Chromosomes are replicated, DNA synthesis takes place
• G2 Phase


  Organelles and molecules required for cell division are produced
• Mitosis


  A process of cell duplication, in which one cell divides into two genetically identical daughter cells
• Stages of Mitosis


  • Prophase

  Metaphase

  Anaphase

  Telophase

  Cytokinesis
• Prophase


  Nuclear envelope disappears, chromosomes condense, spindle forms
• Metaphase


  Chromosomes move to the equator of spindle, each chromatid is attached to spindle with centromere
• Anaphase


  Centromeres split, sister chromatids are pulled apart to opposite poles of the cell
• Telophase


  Nuclear envelopes reform, chromosomes begin to uncoil
• Cytokinesis

  Cytoplasm divides, two new daughter cells are now separate
• Meiosis


  A special type of cell division where the cell undergoes two rounds of cell division to produce four daughter cells, each with half the chromosome number as the original parent cell and with a unique set of genetic material
• Sexually reproducing organisms undergo meiosis to produce haploid gametes in preparation for sexual reproduction
• Meiosis plays an important role in maintaining the chromosome number. In this process the chromosome number is reduced into half so that when the gametes cells (egg and sperm) unite, upon fertilization the chromosome number normally remains the same with the species. It does not double or triple for every generation because any alteration in the process may result in species genetic disorder.
• 46 Chromosome, 44 - Body chromosomes, 2 - Sex cell