LECTURE PRESENTATIONS For CAMPBELL BIOLOGY, NINTH EDITION Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson Chapter 12 Lecture slides also by: Kim Foglia and Kelly Riedell The Cell Cycle

Lectures by Erin Barley Kathleen Fitzpatrick 2011 Pearson Education, Inc. Cell Division The ability of organisms to produce more of their own kind best distinguishes living things from nonliving matter unicellular organisms = division of one cell reproduces the entire organism

Multicellular organisms depend on cell division for Development from a fertilized cell Growth Repair Cell division is an integral part of the cell cycle 2011 Pearson Education, Inc. Figure 12.2

100 m (a) Reproduction 200 m (b) Growth and development 20 m

(c) Tissue renewal Mitosis or Meiosis? Most cell division results in daughter cells with identical genetic information, DNA = MITOSIS Eukaryotic cell division consists of Mitosis, the division of the genetic material in the nucleus Cytokinesis, the division of the cytoplasm The exception is meiosis, a special type of division that can

produce sperm and egg (gametes) cells = MEIOSIS Meiosis yields nonidentical daughter cells that have only one set of chromosomes, half as many as the parent cell 2011 Pearson Education, Inc. VOCAB: Vocab to know: Genome- entire complement of genetic material

Eukaryotic chromosomes consist of chromatin, a complex of DNA and protein that condenses during cell division Somatic cells (nonreproductive cells) have two sets of chromosomes Gametes (reproductive cells: sperm and eggs) have half as many chromosomes as somatic cells 2011 Pearson Education, Inc.

More Vocab to know: DNA must duplicate to get ready to divide Each duplicated chromosome has two sister chromatids (joined copies of the original

chromosome), which separate during cell division The centromere is the narrow waist of the duplicated chromosome, where the two chromatids are most closely attached

During division two sister chromatids of each duplicated chromosome separate. Once separate, the chromatids are called chromosomes 2011 Pearson Education, Inc. Phases of the Cell Cycle The cell cycle consists of

Mitotic (M) phase (mitosis and cytokinesis) Interphase (cell growth and copying of chromosomes in preparation for cell division) 2011 Pearson Education, Inc. Interphase Interphase (about 90% of the cell cycle) can be divided into subphases

G1 phase (first gap) S phase (synthesis) G2 phase (second gap) The cell grows during all three phases, but chromosomes are duplicated only during the S phase 2011 Pearson Education, Inc. Some can return to cycle with signal

(Ex; Liver cells respond to injury) Some never divide again (Ex: Mature nerve, muscle cells) Mitosis Mitosis is conventionally divided into five phases

Prophase Prometaphase Metaphase Anaphase Telophase Cytokinesis overlaps the latter stages of mitosis 2011 Pearson Education, Inc. Figure 12.7a

Prophase G2 of Interphase Centrosomes (with centriole pairs) Chromatin (duplicated)

Early mitotic spindle Plasma membrane Nucleolus Nuclear envelope

Aster Centromere Chromosome, consisting of two sister chromatids Prometaphase Fragments of nuclear

envelope Kinetochore Nonkinetochore microtubules Kinetochore microtubule

Figure 12.7b Metaphase Anaphase Metaphase plate Spindle

Centrosome at one spindle pole Telophase and Cytokinesis Cleavage furrow Daughter chromosomes

Nuclear envelope forming Nucleolus forming More Vocab:

The mitotic spindle -made of microtubulescontrols chromosome movement The spindle includes: the centrosomes, the spindle microtubules, and the asters An aster (a radial array of short microtubules) extends from each centrosome

Kinetochores are protein complexes associated with centromeres microtubules shorten by depolymerizing at their kinetochore ends

Metaphase plate: an imaginary structure at the midway point between the spindles two poles 2011 Pearson Education, Inc. Cytokinesis: A Closer Look Cytokinesis begins during anaphase or telophase and the spindle eventually disassembles

In animal cells, cytokinesis occurs by a process known as cleavage, forming a cleavage furrow In plant cells, a cell plate forms during cytokinesis 2011 Pearson Education, Inc. Figure 12.11

Nucleus Chromatin condensing Nucleolus 1 Prophase Chromosomes

2 Prometaphase 3 Metaphase Cell plate 4 Anaphase 10 m 5 Telophase

MODIFIED from a slide show by Kim Foglia http://www.explorebiology.com/documents/37Ch12MitosisRegulation2005a.pdf Cyclin-dependent kinases (Cdks) are present all the time but inactive unless combined with cyclins KINASESEnzymes that work by adding a phosphate group

to other molecules Presence of MPF triggers passage past G1 & G 2 checkpoints Cyclin levels change throughout cell cycle Fluctuating levels

of different Cyclin-Cdk complexes seem to control all stages of cell cycle Stop and Go Signs: Internal and External Signals at the Checkpoints An example of an internal signal is that kinetochores not attached to spindle microtubules

send a molecular signal that delays anaphase Some external signals are growth factors, proteins released by certain cells that stimulate other cells to divide 2011 Pearson Education, Inc. Figure 12.18 EXTERNAL SIGNAL

Scalpels 1 A sample of human connective tissue is cut up into small pieces. 2 Enzymes digest the extracellular matrix, resulting in

a suspension of free fibroblasts. Petri dish 3 Cells are transferred to culture vessels. Without PDGF

For example, plateletderived growth factor (PDGF) stimulates the division of human fibroblast cells in culture 4 PDGF is added to half the vessels.

With PDGF 10 m Cancer cells exhibit neither density-dependent inhibition nor anchorage dependence CANCER CELLS

Dont respond to control signals Lose density-dependent inhibition Lose anchorage dependence Telomerase enzymes maintain/replace telomeres Transformationprocess that changes a normal cell into a cancer cell

Telomeres protect DNA from being degraded Telomeres become shorter with each replication; shorter in older cells Telomerase enzyme lengthens telomeres Cancer cells have increased telomerase activity 2009 Nobel Prize Physiology/Medicine Discovery of Telomeres

Jack Szostak Carol Greider Elizabeth Blackburn. Most cells divide 20-50 times in culture; then stop, age, die Cancer cells are immortal -HeLa cells from a tumor removed from a woman (Henrietta Lacks) in

1951 are still reproducing in culture http://www.sanger.ac.uk/Info/Press/gfx/081223_cells_300.jpg Loss of Cell Cycle Controls in Cancer Cells Cancer cells do not respond normally to the bodys control mechanisms Cancer cells may not need growth factors to grow and divide They may make their own growth factor

They may convey a growth factors signal without the presence of the growth factor They may have an abnormal cell cycle control system 2011 Pearson Education, Inc. Cancer cells that are not

eliminated by the immune system form tumors, masses of abnormal cells within otherwise normal tissue If abnormal cells remain only at the original site, the lump is called a benign tumor

Malignant tumors invade surrounding tissues and can metastasize, exporting cancer cells to other parts of the body, where they may form additional tumors

Binary Fission in Bacteria Prokaryotes (bacteria and archaea) reproduce by binary fission In binary fission, the chromosome replicates (beginning at the origin of replication), and the two daughter chromosomes actively

move apart 2011 Pearson Education, Inc. Figure 12.12-4 Origin of replication E. coli cell

1 Chromosome replication begins. 2 Replication continues. 3 Replication finishes. 4 Two daughter

cells result. Cell wall Plasma membrane Bacterial chromosome Two copies of origin Origin

Origin The Evolution of Mitosis Since prokaryotes evolved before eukaryotes, mitosis probably evolved from binary fission Certain protists exhibit types of cell division that seem intermediate between binary

fission and mitosis 2011 Pearson Education, Inc. VOCAB REVIEW Figure 12.UN04 Figure 12.UN06

Figure 12.UN05

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