The Cell Cycle, Mitosis, and Cancer Glencoe Biology Chapter

What causes cancer? Cancer is caused by mutations, which creates abnormal cell growth. A mutation is a change to an organism’s genetic material. In our case, DNA. CARCINOGENS: Agents that cause cancer.

What causes mutations. (changes our DNA What causes mutations? (changes our DNA?) Agents of Mutations = “MUTAGENS” Radiation UV radiation X rays Chemicals Alcohol Tobacco Drugs Infectious agents Viruses like HPV

Genetic Material Chromatin: Chromatin = DNA that is long and tangled Chromatin coils up (during M phase) to form chromosomes When UNCOILED: chromatin can start the process of making proteins and can replicate itself When COILED: cell division can occur

Anatomy of a Chromosome

Chromosome = duplicated, coiled DNA CENTROMERE CHROMATID CHROMATID

The Cell Cycle: The “lifetime” of a cell Cells go through THREE (3) periods One of growth and synthesis of DNA One in which the nucleus divides One in which the cytoplasm divides

The Cell Cycle growth period: INTERPHASE G1, S, G2 G1, G2: cell Grows S: DNA Synthesis (duplicates) INTERPHASE S (DNA synthesis) G1 Mitosis G2 Cytokinesis MITOTIC (M) PHASE

The Cell Cycle NUCLEAR DIVISION: MITOSIS the cell’s nucleus and genetic material DIVIDE. Prophase, Metaphase, Anaphase, and Telophase (PMAT) INTERPHASE S (DNA synthesis) G1 Mitosis G2 Cytokinesis MITOTIC (M) PHASE

The Cell Cycle CYTOKINESIS: The cytoplasm divides, creating a new cell M-PHASE: MITOSIS + CYTOKINESIS INTERPHASE S (DNA synthesis) G1 Mitosis G2 Cytokinesis MITOTIC (M) PHASE

So what does this have to do with cancer? The cell cycle has 3 main checkpoints If a cell receives a go-ahead signal at the G1 checkpoint, it will continue dividing If the cell does not receive the go- ahead signal, it will exit the cycle and not divide Tumors form due to out of control cell division cancer cells video discovery of cell cycle video G1 checkpoint Control system S G1 M G2 M checkpoint G2 checkpoint

Mitosis Nucleus Chromatin condensing 10 µm Nucleolus Chromosomes Cell plate Prophase. The chromatin is condensing. The nucleolus is beginning to disappear. Although not yet visible in the micrograph, the mitotic spindle is starting to form. Prometaphase. We now see discrete chromosomes; each consists of two identical sister chromatids. Later in prometaphase, the nuclear envelope will fragment. Metaphase. The spindle is complete, and the chromosomes, attached to microtubules at their kinetochores, are all at the metaphase plate. Anaphase. The chromatids of each chromosome have separated, and the daughter chromosomes are moving to the ends of the cell as their kinetochore micro- tubules shorten. Telophase. Daughter nuclei are forming. Meanwhile, cytokinesis has started: The cell plate, which will divide the cytoplasm in two, is growing toward the perimeter of the parent cell.

Why do cells need to divide? unicellular organisms: REPRODUCTION Multicellular organisms depend on cell division for: Growth Repair

LE 12-6ca G2 OF INTERPHASE PROPHASE PROMETAPHASE

LE 12-6da 10 µm METAPHASE ANAPHASE TELOPHASE AND CYTOKINESIS

INTERPHASE – BEFORE MITOSIS

1st stage of Mitosis: Prophase Chromatin coils up into visible chromosomes nucleus disappears Centrioles begins to separate

2nd Stage of Mitosis: Metaphase Spindle fibers pull the chromosomes to the middle (equator/metaphase plate) of the cell

3rd stage of Mitosis: Anaphase During Anaphase… Chromosomes are pulled apart forming chromatids. chromatids move towards opposite sides of the cell.

4th stage of Mitosis: Telophase chromatids uncoil, becoming chromatin nuclear envelope reforms Mitosis is COMPLETE!!!

Cytokinesis: last stage in the cell cycle cytoplasm divides into 2 new cells ANIMAL CELLS: The cell membrane will move inward and pinch apart PLANT CELLS: A new cell wall forms between the two new cells (CELL PLATE)

SUMMARY - MITOSIS Number of ROUNDS of cell divisions: 1 Number of daughter cells : 2 Genetically identical? Yes Chromosome #: Same as parent Where: Somatic cells (non-sex cells) When: Throughout life Role: Growth and repair

The complete CELL CYLCLE M-PHASE (mitosis + cytokinesis) MITOSIS

VOCABULARY ! Human chromosome number: 46 in body cells (diploid OR 2N) 23 in sex cells (haploid OR N) A picture of species’ full set of chromosomes is a KARYOTYPE