Lecture 9 - Mitosis and Cancer

Cells come from other cells: 

• Growth 

• Replacement 

Three Main Steps: 

1. DNA replication.

2. Mitosis: division of the parent cell’s nucleus and chromosomes.

3. Cytokinesis: division of the parent cell into two daughter cells.

Deoxyribonucleic acid (DNA):

primary information bearing molecule of life:

DNA

• Two chains of nucleotides linked together to form a double helix.

• Nucleotide: nitrogenous base attached to a five-carbon sugar (ribose) and a phosphate molecule.

• Complementary base pairs:

  •  Adenine and Thymine.

  • Guanine and Cytosine.

DNA & Chromosomes: 

• Gene

• Chromatin

• Chromosomes

• Chromosomes

  • Genome

  • Karyotype

Gene

• A specific section of DNA that contains information necessary to produce protein. 

Chromatin

• Linear strand of DNA wrapped around histones 

  • Histones: proteins that keep DNA from getting tangled 

Chromosomes: 

• A compact strand of DNA 

• Genome: 

  • Complete collection of an organisms genetic information 

• Karyotype 

  • Pictorial arrangement of chromosomes 

Haploid: 

• Cells with a single copy of each chromosome 

  • Gamete: sex cell 

    • Egg & sperm 

Diploid: 

• Cells with 2 copies of each chromosome, one maternal, and one paternal 

  • Somatic cells: cells forming the body of the organism 

Percentage of Coding DNA 

• Many organisms have large portions of DNA that do not code for proteins & have no known purpose.

  • Only 1-2% of human DNA codes for proteins 

DNA Replication: 

1. DNA of unduplicated chromosomes unwinds.

2. New DNA nucleotides join with each individual DNA strand to form a new double helix.

3. Duplicated DNA results in duplicated chromosomes.

   1. Sister chromatids.

   2.  Centromere.

Helicase: 

• Enzyme that unwinds DNA separating it into 2 complementary strands 

DNA Polymerase: 

• Enzyme that creates the complementary strand by adding new DNA nucleotides to the template strand 

Mitosis Phases

• Interphase (3 parts) 

• Mitosis: Prophase 

• Mitosis: Metaphase 

• Mitosis: Anaphase 

• Mitosis: Telophase & Cytokinesis 

Interphase (3 parts) 

• G1 (gap 1 phase) = growth & normal functions. 

• S (synthesis phase) = DNA (chromosome ) replication 

• G2 (gap 2 phase) = growth & normal functions continue 

  • Centrosomes develop

Mitosis: Prophase 

• Chromatin condenses to form chromosomes 

• Nuclear membrane & nucleolus disappear 

• Chromosomes: 

  • Two chromatids with centromere 

• Mitotic Spindles form

  • Microtubules

Mitosis: Metaphase 

• Centrosomes at opposite poles 

• Microtubules attach to sister chromatids 

• Chromosomes line up on the metaphase plate.

Mitosis: Anaphase 

• Duplicated chromosomes (sister chromatids) are pulled apart by spindle fibers 

• One full set of chromosomes goes to one end of the cell & one set goes to the other end.

Mitosis: Telophase & Cytokinesis 

Reverse of Prophase: 

• Nuclear envelopes reform around chromosomes 

Cytokinesis: 

• Animal cells: 

  • Cleavage furrow 

• Plant cells: 

  • Cell plate 

Cancer Cells

• Cancer = Unregulated cell multiplication, which invade nearby tissues or other parts of the body, destroying working tissues 

Characteristics of Cancer Cells 

• Membrane proteins have reduced adhesive properties.

• No contact inhibition;

• Indefinite cell division: 

• T-cell deactivation:

Membrane proteins have reduced adhesive properties.

•  Malignant tumors.

No contact inhibition;

• Lumped arrangement as opposed to a single layer 

Indefinite cell division: 

• Cancer cells can divide unlimited number of times 

T-cell deactivation:

• Cancer cells have membrane proteins that turn off some immune system cells called T-cells 

• This prevents T-cells from finding & killing cancer cells 

Chemotherapy: 

• Treatment using drugs that either kill cancer cells or keep cancer cells from dividing 

  • Drugs designed to attack fast dividing cell 

    • Prevent DNA replication 

    • Prevent transcription 

    • Inhibit microtubule formation 

    • Alter mitochondria & transcription

Radiation Therapy: 

• Ionizing radiation used to damage the DNA of cancer cells which prevents them from replicating 

  • Is radiation caused by high energy particles that cause electrons to detach from atoms or molecules 

    • Radiation can be administered externally or internally 

Surgery: 

• Surgeons remove cancerous cells or tumors from the body 

  • Cryosurgery: extreme cold used to destroy cancerous tissue. 

  • Hyperthermia: extreme heat used to damage & kill cancerous cells 

  • Lasers: precision lasers used to cut through cancerous tissue 

Immunotherapy: 

• Drugs that contain protein inhibitors that prevent the cancer proteins from binding with the t-cell receptors, which allows t-cells to destroy cancer cells.