Campbell Biology 14Th Ed Chapt 12

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Cancer cells exhibit neither...

Back 1

Anchorage or density dependent cells

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Cell division

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Continuity of life, reproduction of cells

Multicellular eukaryotes depend on cell division ( development from fertilized egg, growth, repair)

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The life of a cell from formation to its own

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Cell cycle

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Genome

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All the DNA is a cell

Single DNA molecule in prokaryotes

Multiple DNA molecules in eukaryotes

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Chromosomes

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Packaging of DNA molecules

Consist of chromatin (complex of DNA and protein that condenses during cell division)

Eukaryotic species have a specific number of chromosomes in each cell nucleus

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Somatic cells

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Non-reproductive cells, body cells

Have 2 sets of chromosomes

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Gametes

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Reproductive cells (sperm and egg)

Have half as many chromosomes as somatic cells

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Each duplicates chromosome has two..

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Sister chromatids

Joined by cohesins along their lengths

The centromere, the waist, is where the 2 chromatids are mostly attached

Outsid of the centimeter are the “arms”

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During cell division, the 2 sister chromatids separate and move..

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Into two nuclei

Once separated, they are called chromosomes

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Mitosis

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The division of genetic material in the nucleus

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Cytokinesis

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The division of the cytoplasm

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Gamates are produced by a variation of cell division called...

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Meiosis

Meiosis yields nonidentical daughter cells that have half as many chromosomes as the parent cell

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Walter flemming

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1882: developed dyes to observe chromosomes during mitosis and cytokinesis

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Interphase

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About 90% of cell cycle

In 3 phases: G1(fist gap), S(synthesis and half the time of the whole process), G2(second gap)

Cell grows during all 3

Chromosomes are duplicated only during s phase

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Mitotic phase

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Shortest part of cell cycle

Includes 5 stages:

Prophase, prometaphase, metaphase, anaphase, telophase/cytokinesis

PPMAT

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G2 of interphase

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Nuclear envelop around one or more nuclei

2 centrosomes (contains 2 centrioles) formed by duplication of a single centrosome (organize microtubles of spindle)

Chromosomes duplicate during a phase(cannot be seen bc they have not condensed)

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Prophase

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Chromatid condense (can see chromosomes)

Nucleus disappears

Duplicated chromosomes appear as 2 sister chromatids

Mitotic spindle begins to form(composed of centrosomes and microtubles that extend from them)

Shorter microtubles are called aster (stars)

Centrosomes move away from each other

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Prometaphase

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Nuclear envelope fragments

Microtubles invade area

Chromosomes more condensed

Kinetochore protein has formed at centromere of each chromatid (some microtubles attach jerking chromosomes back and forth)

Nonkinetochore microtubles interact with opposite ones lengthening cell

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Metaphase

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Centrosomes are at opposite poles

Chromosomes are at metaphase plate

Each chromosome attached by kinetochore

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Anaphase

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Shortest stage

Cohesin proteins are cleaved, sister chromatids part

Begin moving to opposite ends as microtubles shorten

Cell elongates

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Telephase

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2 new daughter nuclei form

Nuclear envelope arise from fragments of parent cell

Nucleoli appear

Remaining spindle are depolymerized

Mitosis is complete

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Cytokinesis

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Division of cytoplasm is happening while end of telophase

In animal cells, cytokinesis creates cleavage furrow which pinches cell in two

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Mitotic spindle

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Structure made of microtubles that controls chromosome movement during mitosis

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Cleavage

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Cytokinesis

Cleavage Furrow is a groove in cell surface near metaphase plate

Ring of actin microfilaments and protein myosin interact causing the ring to contract like a drawstring and pinch the cell in two

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Cytokinesis in plant cells

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Do not have cleavage

Vesicles create cell plate and fuse

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Binary fission

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Division in half

Asexual reproduction of single -celled eukaryotes (amoeba)

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Origin of replication

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In bacteria, process of cell division is started when the DNA of the chromosome begins to replicate at a specific place on the chromosome

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Evolution of mitosis

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Prokaryotes evolved before eukaryotes, mitosis evolved from binary fission

Certain protist exhibit types of cell division similar to both binary fission and mitosis

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The eukaryotic cell cycle is regulated by a

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Molecular control system

Freq of cell division varies with type of cell (ie: skin cells vs liver cells)

These difference result from differences at molecular level

Cancer cells manage to escape usual controls

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Cell cycle control system

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Molecules in cell that both trigger and coordinate key events ( washing machine analogy)

Single cell with 2 nuclei were fused while in different phase (g1, s, g2). Nucleus of this phases immediately changed to match other phase of cell due to molecules in cells.

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Checkpoints

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Cell cycle stops until go ahead signal is given

Both internal and external checkpoints

ie: washermachine( internal sensor knows when to drain water) external button to push to start cycle

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Types of regulatory proteins involved in cell cycle control...

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2: protein kinase and cyclins

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Cyclin

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Cyclically fluctuating concentration in cells

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Centrosome

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Has 2 centrioles

Where assembly of spindle mictoTs begins

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Cyclin-dependent kinase

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Cell cycle Kinases often inactive in a constant concentration in cell

To be active they must attach to cyclin

Activity of Cdks rises and falls with Chan s in concentration of its cyclin partner

MPF is a cyclin-Cdk conplex

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Maturation-promoting factor (MPF)

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M-phase promoting factor also

Triggers cells passage from G2 checkpoint into m phase

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Process of cell cycle involving MPF complex

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1. Cyclin in s phase thru G2.

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G0 phase

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Non dividing state of cell

If cell down not receive go-ahead signal, it will revert back to this state

Neurons and muscles cells are in this state

Liver cells are until a message from outside as a result of injury is called in

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How many checkpoints are in the cell cycle?

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3: G1(most important), G2, and M phases

If cell receives a go-ahead signal at G1, it will usually complete the process

If not, it will exit and go to G0

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Example of an internal factor checkpoint

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Cells do not begin anaphase until all chromosomes are properly attached to the spindle

This ensures that daughter cells have the correct number of chromosomes

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External factors for checkpoints

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Include growth factors: proteins that stimulate other cells to divide

ie: platelet derived growth factor (PDGF)

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Experiment involving PDGF

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PDGF is required for division of fibroblasts (connective tissue cell)

Fibroblasts have receptors (RTKs) for PDGF that trigger signal transduction pathway that allows the cells to bypass the G1 checkpoint and divide.

Platelets use this to help wounds heal

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Density-dependent inhibition (external factor)

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Crowded cells stop dividing

Cells divide until they form a single layer

If cells are removed from layer, cells start dividing again until space if filled

An external signal is sent out from one cell as to divide or not divide

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Anchorage dependence (external factor)

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For cell to divide, it must be attached to a substratum such a extra cellular matrix of a tissue

Plasma membrane proteins and cytoskeleton help in signals

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During prometaphase, some spindle microtubles attach to _____ and move

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Attach to kinetochores of chromosomes and begin to move them

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Cancer cells exhibit neither...

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Anchorage or density dependent cells

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Cancer cells and growth factors

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Do not need growth factors to divide

May make their own or may convey a growths factors signal without the presence of one

Transform or become “immortal”

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Transformation

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Cells that acquire the ability to divide indefinitely

Must have continual supply of nutrients

Normal cells divide about 20-50 times and die. Cancer cells evade normal controls for apoptosis when something is w

ie: cells from a tumor of Henrietta Lacks (HeLa cells) reproducing since 1951

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Benign tumor

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Cell is recognized by immune system but evades apoptosis

Forms masses of abnormal cells in healthy tissue

Stays at original site due to having too few genetic and cellular changes to survive at another site

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Malignant tumor

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Tumor whose genetic and cellular changes enable them to spread to new tissues (metastasis), impair functions of organs

Cancer

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Metastasis

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Spread of cancer cells to locations distant from their original site

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Cancer cells...

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Unusual number of chromosomes

Metabolism may be altered

Abnormal changes on cell surface cause to lose attachments to other cells and matrix, (able to spread)

Secrete signal molecules that cause blood vessels to grow toward tumor

Cells can separate from tumor, enter blood vessels and lymph vessels, and travel to other parts of the body

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Treating cancer: radiation

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High energy radiation:

Damages DNA in cancer cells much more than DNA in normal cells due to cancel cells losing their ability to repair cells

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Treating cancer: chemotherapy

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Drug enter through circulatory system interfere with cell cycle

Taxol:freezes the mitotic spindle, preventing depolymerization and leads to cell death

Side effects are a result of damage to healthy cells (hair loss/follicle cells; nausea/intestinal cells)

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Recent advances in understanding cell cycle, coupled DNA sequence led to..

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Personalized cancer treatment

ie: 20% of breast cancer tumors show high ants of RTKs and estrogen receptors which increase cell division

Chemotherapy with a molecule that blocks HER2 and tamooxifen (proteins for RTK and E)

Leads to increase survival rates

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The spindle includes...

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Centrosomes, microtubles, and asters

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Not essential for cell division...

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Centrioles

A spindle still forms even if they are destroyed by a laser

Plant cells do not have them

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Kinetochore

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Protein complexes associated with centromeres

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In metaphase. The chromosomes are all lined up at the...

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Metaphase plate

A plane midway btw the spindles 2 poles

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Separase

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An enzyme that cleaves the cohesins during anaphase

Separate sister chromatids so they can move along the kinetochore microtubles toward opposite ends of the cell

The microtubles shorten by deploymerizing at their kinetochore ends

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PAC man mechanism

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Motor proteins on kinetochore walk the chromosomes along the microtubles during anaphase

The depolymerization of the microtubles at the kinetochore ends occurs after the motor proteins have passed

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Another mechanism for shortening of the microtubles

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Chromosomes are “reeled” in by motor proteins at the spindle poles

Microtubles depolymerize after after they pass the motor protein