BIOL 113 Chapter 9

benign cancer

A cancerous tumor contained in one organ and not spreading. Can usually be treated effectively with surgery or radiation.

mutation

A change in the nucleotide sequence of DNA (pg 203)

apoptosis

Programmed cell death; often referred to as cellular suicide. (pg 203) Prevents cells from producing more damaged cells.

kinetochore

Proteins located at the centromere that provide an attachment point for microtubules of the mitotic spindle. (pg 199)

What cells divide least often?

Brain cells; they divide slowly or not at all (pg 195)

prophase

Chromosomes coil Nuclear membrane disintegrates Mitotic spindle starts to form: hollow protein fibers and key components of cytoskeleton; made of microtubules

metaphase

Chromosomes line up at the equatorial plate with spindle fibers pulling on them

Cancer kills by...

Crowding out normal cells Invading other organs Secreting poisonous chemicals

S phase (Synthesis)

DNA replication takes place. Each chromosome is replicated to produce two identical sister chromatids. (pg 196)

telophase

Spindle fibers disassemble Nuclear membrane forms around each daughter nucleus Chromosomes uncoil

radiation therapy

The use of ionizing (high-energy) radiation to treat cancer. (pg 207) Severely damages cell molecules and causes rampant DNA damage which causes the cancer cells to die either directly or by triggering apoptosis. Also damages healthy cells. Can have severe side effects; typically more localized than with chemotherapy.

irinotecan

chemotherapy agent (Interferers with DNA replication)

prometaphase

Spindle fibers attach to chromosomes at centromere via kinetochore proteins Chromosomes condense even more

anaphase

Spindle fibers shorten and sister chromatids separate Chromosomes move to opposite poles

chemotherapy

The treatment of disease, specifically cancer, by the use of chemicals. (pg 194) Chemical treatment for metastatic cancers. Most work by interfering with cell division. Usually interferes with DNA replication, chromosome separation. Also damages healthy cells. Can have severe side effects (such as vomiting, bruising, hair loss, and susceptibility to infection). Look to plants as source of drugs: - Taxol, chemotherapy agent: extracted from the Pacific yew tree, Taxus brevifolia

sister chromatids

The two identical DNA molecules that make up a duplicated chromosome following DNA replication. (pg 196-197)

Driving question 3: How are decisions about treatment made for a given cancer patient?

The type of cancer often determines what type of treatment is viable. If it is a benign tumor (contained in one area), surgery or radiation are typically the best options. If it is metastatic cancer (spread throughout body, often in bloodstream), chemotherapy is more effective (often used in combination with radiation and surgery, where applicable). Cancer treating drugs (often derived from plants) are used to interfere with the cell cycle, often preventing division or inducing apoptosis. Chemotherapy and radiation often cause side effects, however, because they do not differentiate between healthy and cancerous cells.

Why do normal, healthy cells divide?

Growth and development, cell replacement, heal wounds (pg 195)

microtubules

Hollow protein fibers that are key components of the cytoskeleton and make up the fibers of the mitotic spindle. (pg 199) Known as "spindle fibers" during mitosis.

What cells divide most often?

Bone marrow cells; they continuously divide to produce new, healthy blood cells (pg 195)

taxol

Extracted from the Pacific yew tree, Taxus brevifolia Interferes with the normal organization of microtubule: prevents microtubules from shortening, chromatids not separated. Most used for ovarian and breast cancer, and also lung cancer. Highly effective, so demand increased. Environmental concerns: yew trees removed from forests; threatening the northern spotted owl. Unusually hydrophobic and virtually insoluble in water, making it difficult to administer intravenously. Eventually found a solute for it and it was ready for testing by 1984. Development of synthetic taxol (Robert Holton). FDA approved for the treatment of ovarian cancer in 1992 and for breast cancer in 1994. Sold and distributed by Bristol Myers. Controversy when they were found to be overcharging by 20x the cost of production. Trade name became Taxol and generic name became paclitaxel.

Driving question 4: How are new cancer drugs developed?

New cancer drugs are developed from plants, usually. Plant extracts are tested for their ability to destroy a variety of cancerous cells. Once a viable drug is found, the plant is cultivated for sufficient supply, related plants with similar effects are also found and cultivated (in the cases of rare original plant species), structure of the compound is used to try to make synthetic versions, and testing is done to learn of the effects of the drugs on the body. Once a safe and effective drug is found, it is put on the market for cancer treatments.

Driving question 2: How do normal cells and cancer cells differ with respect to cell division?

Normal cells have functional checkpoints that ensure that a cell divides properly. Checkpoints make sure that DNA has duplicated properly and that the cell is ready for division. If the cell is not ready for division during the G1 phase, it is moved to the G0 phase, where it will not divide. If there are minor errors in the DNA replication process (during the G2 phase), the cell can fix the errors. If there is irreparable, extensive damage, the cell undergoes apoptosis (cellular suicide). Cancerous cells have issues with their division checkpoints, causing the cells to divide uncontrollably and often with a high mutation rate.

Cancer treatments

Surgery: removes lump of cells Radiation Therapy: - ionizing radiation - kills dividing cells by damaging DNA, triggering apoptosis Chemotherapy Often treated with a combination of all three.

G1 phase (Gap 1)

The cell enlarges, produces additional cytoplasm, and begins to produce new organelles. (pg 196)

Driving question 1: When and how does normal cell division occur in the body?

When: At the end of interphase, provided that new cells are needed for growth, cell replacement, or healing. How: Cells go through three stages of division: interphase, mitosis, and cytokinesis. Interphase takes the most time and it involves the growth of the cell and the duplication of organelles, cytoplasm, and DNA. Mitosis occurs in four stages: prophase, metaphase, anaphase, and telophase. Prophase is the condensing of chromosomes and dissolving of the nuclear envelope. Metaphase is the lining up of chromosomes along the metaphase plate via spindle fibers. Anaphase is the splitting of sister chromatids at the centromere, pulling chromosomes to opposite poles of the cell. Telophase is the formation of identical daughter nuclei. Cytokinesis is the physical splitting of a cell into two identical daughter cells.

centromere

The specialized region of a chromosome where the sister chromatids are joined; critical for proper alignment and separation of sister chromatids during mitosis. (pg 196-197)

metastasis

The spread of cancer cells from one location to another (pg 207) Surgery is not an effective treatment. Best option is usually chemotherapy.

interphase

The stage of the cell cyle in which cells spend most of their time, preparing for cell division. The cell makes a copy of the DNA and produces more organelles and cytoplasm. There are three distinct sub-phases: G1, S, and G2. (pg 196) In a cell that takes approximately 24 hours to divide, this phase takes about 22 hours to complete.

mitotic spindle

The structure that separates sister chromatids during mitosis. (pg 199)

mitosis (M phase)

The segregation and separation of duplicated chromosomes during cell division. (pg 196) Sister chromatids separate at the centromere. Occurs in a series of phases. Takes about 2 hours to complete in cells with a 24-hour cell cycle.

cell cycle checkpoint

A cellular mechanism that ensures that each stage of the cell cycle is completed accurately and cells divide only when necessary. (pg 203) Either has repair mechanisms that fix errors, or induces apoptosis. Checkpoints at G1 phase (is there a signal to divide), G2 phase (have chromosomes replicated properly, is there DNA damage), and metaphase (chromosomes aligned for proper chromatid separation). If cells are not ready at G1, they are shunted to G0.

cancer

A disease of unregulated cell division; cells divide inappropriately and accumulate, in some instances forming a tumor. (pg 194)

tumor

A mass of cells resulting from uncontrolled cell division. (pg 204)

metastatic cancer

Cancerous cells that have entered the blood stream and spread to different parts of the body. Surgery is not an effective treatment. Best option is usually chemotherapy.

G2 phase (Gap 2)

The final preparatory stage, during which the cell prepares for division (pg 196)

cell cycle

The ordered sequence of stages that a cell progresses through in order to divide during its life; stages include preparatory phases (G1, S, G2) and division phases (mitosis and cytokinesis). (pg 195) Dividing of a parent cell into two identical daughter cells.

cytokinesis

The physical division of a cell into two daughter cells. (pg 196) Via cleavage furrow "pinching" in animal cells or via synthesis of a new cell wall in plant cells.

cell division

The process by which a cell reproduces itself; important for normal growth, development, and repair of an organism. (pg 194)