Mills AP Biology 2002-2003 Chapter 9 Cellular Reproduction and the Cell Cycle Read Chapter 9 in Textbook Read pages 85-92 in Cliffs AP (4 th ) Test Book

Mills AP Biology 2002-2003

Chapter 9Cellular Reproduction and the Cell Cycle

Read Chapter 9 in TextbookRead pages 85-92 in Cliffs AP (4th) Test

BookDo Sample Questions #1-16 on pg 93-

94Due Nov 5


Chapter 9Cellular Reproduction and the Cell Cycle

• Topics– 9.1 The Cell Cycle– 9.2 Mitosis and Cytokinesis– 9.3 The Cell Cycle and Cancer– 9.4 Prokaryotic Cell Division


Chapter 9 Cellular Reproduction and the Cell Cycle9.1 Eukaryotic Cell Cycle

• Cell Cycle– Four stages

• M – Mitotic Phase = mitosis and cytokinesis

• G1 – growth• S – DNA replication• G2 – growth

– Different types of cells and different species spend varying amounts of time in each stage

Animation of Cell Cyclesee next slide



Chapter 9 Cellular Reproduction and the Cell Cycle 9.1 Eukaryotic Cell Cycle

Broad Bean



• Cell Cycle Clock– What controls which cells divide and how often?

• Recent research uncovering some of the mysteries• May help with understanding abnormal cell growth – such as

cancer

– Two critical checkpoints where cell has to be signaled to proceed or stop

• G1 stage S stage• G2 stage M stage

– Kinases and cyclins are proteins that help regulate the cell cycle



• Cell Cycle Clock– Kinases

• Enzymes that activate or inactivate other proteins by phosphorylating them

– Removes P from ATP, and adds it to a protein

• Common way for a cell to “turn on” a cellular process

• Kinases used to turn on the cell cycling, but need to be activated themselves first

– Activated by cyclins



• Cell Cycle Clock– Activation of kinases by

cyclins at two critcal checkpoints

• End of G1 stage S stage

• End of G2 stage M stage

– Cause cell to continue cycle

G1 checkpoint

Feedback from the cell determines whether the cell cycle will proceed to the S phase, pause, or withdraw into G0




Chapter 9 Cellular Reproduction and the Cell Cycle9.3 How Eukaryotic Cells Cycle

• Lack of normal control over the cell cycle can lead to conditions such as – Psoriasis (uncontrolled growth of skin cells)– Progeria (early death of cells)– Cancer

John Tacket (1988-2004) – died at age 15. Average life span for a child with progeria is 13yrs. Usually die of heart disease - atherosclerosis

Normal life span for a skin cell is 28-30 days. Psoriasis cells cycle every 6 days and don’t exfoliate.

From Progeria foundation web site: “HGPS (Progeria)is caused by a mutation in the gene called LMNA (pronounced, lamin - a). The LMNA gene produces the Lamin A protein, which is the structural scaffolding that holds the nucleus of a cell together. Researchers now believe that the defective Lamin A protein makes the nucleus unstable. That cellular instability appears to lead to the process of premature aging in Progeria.”


Chapter 9 Cellular Reproduction and the Cell Cycle9.2 Mitosis and Cytokinesis

• Eukaryotic cells– We will look at

multicelluar eukaryotes– Cells divide by two

processes• Mitosis – division of

nuclear material• Cytokinesis – division of

cytoplasm and other organelles

• Together these are called the Mitotic Phase

– We will look first at mitosis


Chapter 9 Cellular Reproduction and the Cell Cycle 9.2 Mitosis and Cytokinesis

• Mitosis– Series of events that divides up

replicated DNA into two identical (genetically) daughter cells.

• First, lets review a little bit about what DNA and chromosomes are.

Mitosis in a plant cell



• Let’s take a closer look at DNA– Where is it?– What is it made of

(chemically)?– What does it do?– What’s a gene?





• DNA refresher

Bases: adenine guanine thymine cytosine uracil



DNA, DNA, DNA, DNA, …


Duplicated DNAin metaphase of mitosissister chromatids

Single chromatid, one double strand of DNAwound around histones (proteins)

Base pairs

Geneone smallsection ofDNAstrand

Sugar and phosphates



• A gene is a particular piece of a strand of DNA, that codes for the production of a particular protein

Geneone smallsection ofDNAstrand



• Stages of Mitosis (nuclear division)– Prophase– Metaphase– Anaphase– Telophase

Cell at end of interphase, before prophase starts.



• Prophase (longest phase)

– duplicated chromosomes condense to form chromosomes– centrioles (animals only)move to opposite sides (poles) of cell– spindle fibers associate with centromeres on chromosomes– nucleolus and nuclear envelope disappear– mitotic spindle forms– Chromosomes start to move towards equator

Centromere connects sister chromatids

Asters



Plant cellAnimal cell

Prophase



• Metaphase– chromosomes align at equator “metaphase plate”– microtubules attached to centromeres align chromatids, start

to pull apart



Metaphase



• Anaphase– centromeres separate– chromatids get pulled to opposite sides (poles)of cell with

help of spindle fibers– cell elongates– shortest phase, lasts a few minutes– cytokinesis begins



Anaphase



• Telophase– chromosomes get to centrioles– spindle fibers and asters disappear– chromosomes start to unwind chromatin– nuclear envelope re-forms– nucleoli re-form– cytokinesis continues



Telophase

Cell Plate



Mader Movie Hard drive ..\..\Biology\Biology Clipart Movies Animations Sounds\Biology movies\Mader VD105 How Chromosomes Separate.MOV


Mitosis Movie 48 sec..\..\Biology\Biology Clipart Movies Animations Sounds\Biology movies\mitosis.mov



• Mitosis is followed by cytokinesis

See also http://www.cellsalive.com/mitosis.htm

*note Metaphase and Anaphase labels

are missing


Another web animation of mitosishttp://www.johnkyrk.com/mitosis.html


Chapter 9 Cellular Reproduction and the Cell Cycle9.2 How Eukaryotic Cells Divide


Daughter nucleus

Nucleoli in nucleus

Vesicles containing cell components, fusing to form cell membrane




• What is the purpose of cell division?– Make duplicate of DNA to pass on– For unicellular organisms (such as bacteria,

paramecium) cell division = asexual reproduction– For multicellular organisms, cell division is used for

growth and repair


Chapter 9 Cellular Reproduction and the Cell Cycle9.3 The Cell Cycle and Cancer

• Cell Cycle and Cancer– What allows cancer cells to grow unchecked into

large, invasive, malfunctioning masses of tissue?– ..\..\Biology\Biology Clipart Movies Animations

Sounds\Biology movies\cell_growth.mpg


Chapter 9 Cellular Reproduction and the Cell Cycle 9.3 The Cell Cycle and Cancer

• Cell Cycle and Cancer– Oncogenes

• Cancer causing genes

• Could these genes control the genes for production of abnormal cyclin ?

• Malfunctioning cyclin could lead to uncontrolled cell growth.

– Tumor Suppressor Genes• Usually prevent cancer• One tumor suppressor

gene (p53 gene) codes for the production of a protein (p53) that binds to cyclin and keeps it from functioning – stopping cell growth.

– Keeps cells with mutated DNA from reproducing, causes apoptosis



• Cell Cycle and Cancer– Abnormal development

of cells = tumor– Tumor develops when

there is failure to control cell growth

– P53 protein (controlled by p53 gene – tumor suppressor gene) is a protein that monitors cell growth and checks DNA for mutations

– Some cancer cells have faulty or no p53



Figure 9.9 Functions of p53.If DNA is damaged by a mutagen, p53 is instrumental in stopping the cell cycle and activating repair enzymes. If repair is impossible, the p53 protein

promotes apoptosis.



• Cell Cycle and Cancer– Apoptosis

• Programmed cell death• Happens all the time• Cell contains enzymes

(caspases) that can destroy the cell

• Enzymes are normally inhibited unless get signals to destroy cell

• Signals can be– External – as in fetal

development – DNA damage initiates cell

death• Tumor cells have high level of

protein survivin which blocks apoptosis – cells don’t die

Indicate cell is undergoing apoptosis



• Characteristics of Cancer Cells– Lack differentiation– Have abnormal nuclei– Form tumors– Undergo angiogenesis and

metastasis– Don’t respond to things that would

normally inhibit cell growth, such as:• Increased cell density (contact

inhibition)• Unanchored cells• Not enough growth hormone


Chapter 9 Cellular Reproduction and the Cell Cycle9.3 Cell Cycle and Cancer

• Cell Cycle and Cancer– PBS Cancer Growth Animation (if time) from:

http://www.pbs.org/wgbh/nova/cancer/grow_flash.html – Hard drive ..\..\Biology\Biology Clipart Movies Animations Sounds\Biology movies\cancer growth pbs.swf


Chapter 9 Cellular Reproduction and the Cell Cycle9.4 How Prokaryotic Cells Divide

• Prokaryotic Cells– What are they? Who has them?– Divide (asexually) by a process called binary fission

• How does binary fission work?– Bacterial Fission Movie

» ..\..\Biology\Biology Clipart Movies Animations Sounds\Biology movies\bacterial fission.mov


Chapter 9 Cellular Reproduction and the Cell Cycle 9.4 How Prokaryotic Cells Divide

• Binary Fission– Simplest form of asexual

reproduction– Parent divides into 2

approximately equal parts

– Both have identical DNA– Bacteria and some

protozoa (ameba, paramecium) use this method

Paramecium fission


Chapter 9 Cellular Reproduction and the Cell Cycle 9.4 How Prokaryotic Cells Divide

• Binary fission – bacteria– Single chromosome

(DNA) in loop shape, attached to plasma membrane

– DNA replicates– Cell elongates and

eventually separates– Can happen very

rapidly in certain bacteria under the right conditions

E.coli, under the right conditions, can divide every 20 minutes. How many bacteria

would be possible from a single bacteria in 7 hours?

Over one million!!

Bacterial Fission Movie»Hard drive ..\..\Biology Clipart and sounds\Biology movies and animations\bacterial_division.mpeg


THE END

Additional siteshttp://www.hhmi.org/biointeractive/cancer/animations.html

http://www.hhmi.org/biointeractive/cancer/p53/01.html

Read Connecting the Concepts and Big Ideas page

167

Documents

Mills AP Biology 2002-2003 Chapter 9 Cellular Reproduction and the Cell Cycle Read Chapter 9 in Textbook Read pages 85-92 in Cliffs AP (4 th ) Test Book