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Cellular Division. Chapters 6, 27, and 42-43. Objective 1: Structure of Chromosome. DNA is coiled around histone proteins Appears like beads on a string It is then coiled further around the existing coils Also called a “ supercoil ”. Some definitions to help understand.

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cellular division

Cellular Division

Chapters 6, 27, and 42-43

objective 1 structure of chromosome
Objective 1: Structure of Chromosome
  • DNA is coiled around histone proteins
    • Appears like beads on a string
  • It is then coiled further around the existing coils
    • Also called a “supercoil”
some definitions to help understand
Some definitions to help understand
  • Homologous Chromosomes- chromosomes that are similar in size, shape, and genetic information.

Chromosomes are made of 2 essential parts

  • 1. Chromatid- 2 copies per chromosome
  • 2. Centromere- Protein disk that connect the two chromatids
objective 2 terms
Objective 2: Terms
  • Haploid- 1 set of chromosomes, 23 chromosomes per cell (egg or sperm) AKA Sex cells. Symbol n
  • Diploid- 2 sets of chromosomes, 46 per cell, Somatic cells or body cells. Symbolized by 2n.
  • Gamete- Germ cell, sex cell, eggs and sperm= 23 chromosomes each.
  • Zygote- (Fertilized egg), sperm unites w/ egg= 46 Chromos
objective 3 cell cycle
Objective 3: Cell Cycle
  • G1- Growth and F(x) of cells. Cell prepares for DNA Replication. (Cancer cells skip this phase).
  • S- Chromosome/DNA replication
  • G2- Organelles replicate to prepare for cell division by acquiring proper proteins.
  • M- (Mitosis)(Nuclear Division) Prophase, Metaphase, Anaphase, Telophase.
  • C- (Cytokinesis)(Cytoplasmic division) Cleavage furrow or cell plate.
objective 4 cell division stages
Objective 4: Cell Division Stages
  • Interphase
    • G1, S, G2
    • Chromatin- Uncoiled, working DNA
    • Cell is functioning
    • DNA replication
    • Preparations for division
  • Nuclear Membrane dissolves and breaks down.
  • Chromatin condenses and become visible Chromosomes.
  • Centrioles (hollow, barrel shaped cell structure) move to opposite poles and a network of spindle fibers form.
  • Paired chromosomes (Chromatids) line up in the middle (equatorial plane).
  • Spindles attached to each chromosome at centromere, which are already connected to the centrioles.
  • Centromere divides and chromosomes physically split
  • Spindle fibers contract and shorten, pulling the chromosome to the opposite poles.
  • Mirror images- Equatorial division
  • Chromosomes arrive at opposite poles and spindles disappear.
  • Nuclear envelope reforms
  • Chromosomes uncoil to become working chromatin again
  • Cytokinesis begins
    • Plants= Cell wall
    • Animals= Cleavage furrow
objective 5 cancer
Objective 5: Cancer


  • 4 Theories
    • Standard Dogma, Modified Dogma, Early Instability, All- Aneuploidy
    • All result in mutations that cause oncogenes to be turned on and tumor suppressor genes to be turned off.
    • Oncogenes- Stimulate growth AKA Cell division.
    • Tumor suppressor genes- restrain cells’ ability to divide.
4 theories
4 Theories
  • Standard - result in mutations that cause oncogenes to be turned on and tumor suppressor genesto be turned off
  • Modified – something disables the repairing of DNA
  • Early instability – “master genes” silenced
  • Aneuploidy– too many or too few genes
development of cancer
Development of Cancer
  • Initiation- a mutation occurs to usually 1 (or more) genes. Lag time to next stage= 20-25 years.
  • Promotion- Anything that happens that leads to expression of the mutation. Such as cells dividing too quickly.
  • Progression- tumor grows larger and larger, tumor produces enzymes and polypeptides that direct blood to tumor.
cancer characteristics
Cancer Characteristics

6 common characteristics to all deadly cancers

  • Growth w/out a go signal
  • Growth even against stop signals
  • Evades autodestruct signals
  • Ability to stimulate blood vessel construction
  • Immortality
  • Metastasis- Ability to spread to new tissue.
cancer treatments
Cancer Treatments
  • Many are specific to a particular type of cancer. Others can work on a number of cancer types. Most treatments try to work by killing cancerous cells.

Common Treatments:

  • Radiation- malignant tumors
  • Chemotherapy- Kills cells that rapidly divide
  • Surgery- Removing the tumor
  • Hormone therapy- Manipulates endocrine system
treatment continued
Treatment continued…

Benefits: Kill cancer cells.

-RNAi– siRNA Turn off Oncogenes

-Potentially Perfect Cure

Drawbacks: Illness

Radiation- can’t pinpoint cancer cells.

Chemo- targets all dividing cells.

Surgery- may not get all cells.

Hormone- can mess up your body’s systems.

How can cancer kill you? Handout

objective 6 pictures
Objective 6: Pictures

Lab time baby!

objective 7 meiosis
Objective 7: Meiosis


Meiosis: I, P, M, A,T M= Crossing Over

Meiosis II: P, M, A, T

Overview of Meiosis I and Meiosis II

Meiosis I: Homologous chromosomes separate into 2 haploid cells.

Meiosis II: Similar process to mitosis. 2 haploids become 4 haploid cells.

purpose of meiosis
Purpose of Meiosis
  • Production of gametes or sex cells (eggs and sperm)
  • Each 1 contains the haploid number of chromosomes
importance of meiosis
Importance of Meiosis
  • The offspring have the correct diploid chromosome number
  • Sex provides for combination of genes= better survival
    • AKA: Genetic Recombination
objective 8 mitosis vs meiosis
Objective 8: Mitosis vs. Meiosis



  • 1 cell -> 2 cells
  • Maintain chromosome #
    • Diploid
  • Produce body cells
  • Identical cells
  • 1 cell -> 4 sperms

1 egg (3 polar bodies)

  • Reduce chromosome #
    • Haploid
  • Produce sex cells
  • Cells are different
objective 9 sexual vs asexual
Objective 9: Sexual vs. Asexual



  • Advantages
    • Diversity
    • Genetic recombination
  • Disadvantages
    • Few offspring
    • Energetically unfavorable
  • Advantages
    • Tons of offspring
    • Don’t need anybody else
  • Disadvantages
    • No diversity= little evolution
    • Limited Environment
objective 10 evolutionary developments
Objective 10: Evolutionary developments
  • Multicellular
  • Tissues
  • Bilateral Symmetry
  • Body Cavity
  • Coelom
  • Segmentation
  • Jointed Appendages
  • Deuterostomes
  • Notochord
objective 11 embryonic development
Objective 11: Embryonic development

1st Trimester (1-3 months)

  • Week 1: Cleavage- Results in a hollow ball of calls called a blastocyst
  • Week 2: Gastrulation- Formation of the 3 primary tissues

- Endoderm, Mesoderm, Ectoderm

  • Week 3: Neurulation- Formation of hollow dorsal nerve tube. - Blood vessels begin to form
  • Week 4: Organogenesis- Body Organs forms - The heart begins to beat and limb buds form.
2 nd and 3 rd trimesters
2nd and 3rd Trimesters
  • 2nd Trimester (4-6 months)
    • Morphogenesis- Miniature limbs assume their adult shapes. Organs grow and fully develop.
  • 3rd Trimester (7-9 months)
    • Growth- Fetus can survive if born during this stage.
objective 12 stem cells
Objective 12: Stem cells
  • What are they?
  • Omnipotent cells. They have the potential to develop into any of the cell lines in the body.
  • The most powerful and potentially the most promising for medical are found in very young embryos.
  • Other stem cells are found in bone marrow, umbilical cord blood and in various other places around the body.
importance of stem cells
Importance of Stem cells
  • Use to cure degenerative (organs/tissue deteriorate over time) diseases
    • Alzheimer's
    • Diabetes mellitus
    • Muscular dystrophy
  • Constructing new organs or limbs
problems with stem cells
Problems with Stem cells
  • To get the most potent cells currently requires the use of human embryos.