Bio - Cell Division

• A chromosome is a thread-like

  structure found in the nucleus

  of cells.
• DNA (Deoxyribonucleic Acid) -

  often referred to as the code

  of life because it contains the

  information needed to form

  and control the physical

  makeup and chemical

  processes of an organism.
• Gene is a segment of DNA that

  code for a particular trait.
• The P Arm is upper
• The Q arm is lower (the one below)
• The centromere is the center part of the chromosome
• Sister Chromatids are the Two pairs that make up the Chromosome
• Heterochromatin is the darkly stained region of the Chromosome
• Euchromatin is the lightly stained region of the chromosome
• Chromosome Number
• Chromosome Number

  Human - 46

  Fruit Fly - 8

  Lettuce - 14

  Goldfish - 94
• All cells are derived from preexisting cells
• Cell division is the process by which cells

  produce new cells
• Some tissues must be repaired often such

  as the lining of gut, white blood cells, skin

  cells with a short lifespan
• Other cells do not divide at all after birth

  such as muscle & nerve
• Why is cell division

  important?

  • Repair
  • Growth
  • Heredity
• 2 TYPES of CELL

  DIVISION

  • Mitosis
  • Meiosis
• Cell Cycle – is the series of events that takes place in a cell

  leading to its division and duplication.
• Sequence of Interphase:

  • G1 (Growth)
  • S (DNA Synthesis "replication")
  • G2 (Growth and Preparation for Cell Division
• Somatic cells are any cell in the body except for sex cells
• Cell Division happens after Interphase in the cell cycle
• MITOSIS

  • is the process where cell divides to produce 2 daughter cells.
  • this type of division happens in body cells also known as

  somatic cells or autosomes.

  • the number of chromosomes is the same as those in each of

  the daughter cells

  • the complete set of chromosomes is referred to as diploid;

  diploid parent cell produces 2 diploid daughter cells
• Spindle Fibers from two set of paired Centrioles
• Prophase - The nucleus starts to disappear thereby exposing the

  chromosomes into the cytoplasm
• Telophase - Each cell has an equal and complete number of

  chromosomes on the opposite poles
• Anaphase - The chromosomes start to move towards the opposite

  poles
• Metaphase - The chromosomes are now aligned at the equatorial

  plate
• Interphase - The cell produces cytoplasmic organelles, DNA

  replicates, and synthesizes other cellular organelles

  necessary for mitosis
• CYTOKINESIS - the division of

  the cytoplasm

  form two

  separate

  daughter cells

  immediately

  after mitosis.
• In plant cells,

  cytokinesis occurs when

  a rigid wall, called a cell

  plate, forms between

  the two daughter cells.
• MEIOSIS

  • from a Greek word which means “to make smaller”
  • also called the “reduction-division stage”
  • is a type of cell division that produces sex cells or

  gametes.,

  • is the form of division of the cell nucleus by which a cell

  divides into four "daughter cells" each of which has

  half** of the number of chromosomes of the original

  cell.
• Reduction Stage of Meiosis

  I

  P1

  M1

  A1

  T1
• MEIOSIS 2 (similar to mitosis)

  P2

  M2

  A2

  T2
• Synapsis - pairing of homologous chromosomes
• Tetrad - 4 sister chromatids of paired homologous chromosomes
• "Crossing over" - recombination of alleles in homologous chromosomes
• Crossing Over results to genetic variety in gametes (not the same)
• Leptotene - each chromosome is made up of two long

  threads of sister chromatids as a result of replication during

  interphase.
• Zygotene - pairing of homologous chromosomes takes place

  known as synapsis.
• Pachytene - a tetrad of the chromosomes has formed known

  as a bivalent. This is the stage when crossing over occurs.