Essential Lecture Questions After lecture you should be able to answer… 1. What are the reasons cells undergo mitosis? 2. What are the parts of the cell cycle? In which part does DNA duplicate? In which part does mitosis occur? 3. What are the 4 stages of mitosis? What happens in each stage? 4. What is the end result of mitosis?

The Cell Cycle The Cell Cycle-  During the cell cycle, the cell grows, replicates its DNA, and divides into two daughter cells. G1, S, G2, M Interphase- Cell is growing and preparing for cell division G1 phase S phase – DNA Replication G2 phase Cell Division- (M phase) process of one cell forming two daughter cells. Mitosis- Nuclear division Cytokinesis- cytoplasm division

Figure 12.4 The cell cycle

Interphase (94% of a Cell’s Life) G1 phase Cell increases in size Synthesize new proteins and organelles S phase Chromosomes are replicated here DNA/protein complex G2 phase Many organelles and molecules required for cell division are produced

Definition of Mitosis What is mitosis? Mitosis is the nuclear division and cytokinesis, in eukaryotic cells, producing 2 daughter cells with the same diploid (2n) number of chromosomes (somatic cells).

Types of Cells Somatic Cells- regular body cells (skin, muscle, etc) Diploid (2n)- have two kinds of each chromosome Somatic cells undergo mitosis Gamete (germ) Cells- sex cells (sperm and egg) Haploid (n)- have one kind of each chromosome. Haploid cells will fuse to form a diploid zygote Cells undergo meiosis to form germ cells

Why a Somatic Cell Divides The larger a cell grows, the more demands the cell places on its DNA and the more trouble the cell has moving enough nutrients and wastes across the cell membrane Specific issues a cell has: DNA “Overload” Trouble Exchanging Material – Surface area/to volume ratio Damage to tissues; repair Growth of organism signals mitosis – HGF, steroids

Figure 12.1c The functions of cell division: Tissue renewal

Why a Somatic Cell Divides DNA “Overload” Information is stored in DNA As a cell grows it usually does not make copies of DNA If a cell grew too large an information crisis would occur (not enough DNA to instruct the cell as needed)

Why a Somatic Cell Divides Cellular Transport needs The larger the cell volume: the more food, water, and oxygen needed The more wastes produced Less efficient transport The bigger the cell the greater the distance and more material to get out and in; more volume, less surface area (plasma membrane)

Why a Somatic Cell Divides Surface Area to Volume Cell volume grows quicker than cell surface At some point in time there is not enough surface area for material exchange (ex. food and waste)

Key to cell division is the copying and equal separation of chromosomes…. Chromatin – hazy loose DNA becomes condensed and coiled  chromosomes Chromosome- DNA and proteins that contain genetic information 46 human chromosomes or 23 pairs Sister Chromatids- when chromosomes are replicated and there are 2 identical parts Centromere- part where sister chromatids are attached

Figure 12.3 Chromosome duplication and distribution during mitosis

M phase: Mitosis PMAT Prophase Metaphase Anaphase Telophase PMAT + C = Cell Division

Cell Division (mitosis and cytokinesis) Mitosis (P M A T) C Prophase Metaphase Anaphase Telophase

Mitosis Prophase- 1st and longest phase of mitosis

Mitosis Metaphase- 2nd stage of mitosis

Mitosis Anaphase- 3rd stage of mitosis

Mitosis Telophase- 4th stage of mitosis In animal cells, a cleavage furrow forms

Cell Division (mitosis and cytokinesis) Cytokinesis- usually occurs at the same time as telophase of mitosis In animal cells, a cleavage furrow forms In plants cytoplasm is divided by a cell plate being formed

Cytokinesis Division of the cytoplasm itself Plants lack centrioles Can take place in a number of ways: *in animal cells – “draw-string” effect *in plant cells – cell plate forms from inside out, and cell wall begins to appear

Figure 12.8 Cytokinesis in animal and plant cells

Concept Map of all events of Cell Cycle Section 10-2 Cell Cycle includes M phase (Mitosis) Interphase is divided into is divided into G1 phase S phase Prophase G2 phase Metaphase Telophase Anaphase Go to Section:

Prokaryote vs. Eukaryote Result Multicellular Eukaryotes – Results include growth, repair of specialized cells in a multicellular organism Unicellular Eukaryotes and Prokaryotes – called Cell Division is called Binary Fission What is the result?

http://www.bozemanscience.com/mitosis

Why do some human cells divide often and others not at all?

When cells come into contact with other cells, they stop growing…..

Regulating Cell Division Internal regulators Proteins that respond to events inside the cell Cyclins- regulate the timing of the cell cycle in eukaryotic cells External regulators Closeness of neighboring cells slows growth (no contact inhibition) Protein hormones Ex. Growth factors stimulate growth

Effect of Cyclin on the cell cycle

Role of proto-oncogenes and oncogenes Proto-oncogenes (unmutated oncogenes) stimulate cell division in a regulated manner. Proto-oncogenes include growth factors, growth factor receptors, and cyclins. Oncogenes are mutated forms of these genes that result in unregulated stimulation of cell division.

Cancer

Uncontrolled Cell Growth If growth is not controlled, then crowding and even tissue damage may result Ex. Cancer: disorder where body’s own cells lose the ability to control growth; can crowd and even damage tissue in surrounding area – forms tumor Benign vs. malignant tumors – benign are localized and not spreading; malignant tumors become invasive enough to impair normal function of other organs Also, malignancies are capable of breaking off and starting up in another location -- metastasis

How do malignancies form? Angiogenesis

Cancer Formation DNA Mutations – Carcingens, mutagens - oncogenes Excessive hormones – genetic, environmental Heritable mutations – mutations in cell cycle control genes (Ex: p53) Viral infections – Can insert in DNA and disrupt control over cell cycle (HPV) Mutated receptor proteins – bind hormones too tightly (HER2 Receptor)

HPV & Cervical Cancer

Treatment Surgery: mastectomy (breast cancer), prostatectomy (prostate cancer) etc./can allow staging of the cancer Radiation therapy: use of ionizing radiation that damages genetic material so much that cell can no further divide (normal cells can be affected by radiation as well but can recover) Chemotherapy: cytotoxic drugs targeting all rapidly dividing cells by interfering with phases of the cell cycle Immunotherapy: stimulation of own immune system to destroy cancerous cells – alpha interferon