Chapter 5.2 Notes

• Cells that are not dividing ___________ in the G 1phase– Example:remain• After you are developed some of your_____________ nerve and _______________ muscle cellsstop dividing and replicating…so it is importantto take care of themChapter menuResourcesCopyright © by Holt, Rinehart and Winston. All rights reserved.

G 0• If a cell no longerdivides, sometimesscientist say that it isin the ______ G 0 stage,because it has left thecell cycleChapter menuResourcesCopyright © by Holt, Rinehart and Winston. All rights reserved.

Chapter 6Section 2 The Cell CycleS Phase• Period during which DNA is__________ copied or______________synthesized• To be copied, the DNA mustbe ___________ stretched out, so it iscalled ______________ chromatin• The two identical copies willform the _______________chromatidsin a chromosomeChapter menuResourcesCopyright © by Holt, Rinehart and Winston. All rights reserved.

Chapter 6Section 2 The Cell CycleG 2 Phase (Gap 2)• Other organellesnecessary forreproduction, such as___________ spindle fibers,are made– They consist of_______________microtubulesthat pull apart the_______________chromatidsof chromosomes sothat they can bedivided betweennew cellsChapter menuResourcesCopyright © by Holt, Rinehart and Winston. All rights reserved.

Chapter 6Section 2 The Cell Cycle• After interphase,_______________mitosisoccurs, which issometimes called the_____ M phase• During mitosis, thecopied DNA coils upinto ______________chromosomesChapter menuResourcesCopyright © by Holt, Rinehart and Winston. All rights reserved.

• These chromosomes, are passed onto each new cellwhen the cell divides…but the ______________ nuclear________________ must first disintegrate.envelope– A new nucleus _______________ in each newcell– Due to this occurrence, mitosis is often referred toas ________________ divisionnuclearreformsChapter menuResourcesCopyright © by Holt, Rinehart and Winston. All rights reserved.

Chapter 6Section 2 The Cell Cycle• After mitosis,_________________cytokinesisoccurs• Cytokinesis involvesthe splitting of the_________________cytoplasm• Once cytokinesis iscomplete, the originalcell has divided into_______ 2 new,_____________ identical cellsChapter menuResourcesCopyright © by Holt, Rinehart and Winston. All rights reserved.

Control of the Cell Cycle• How exactly does a cell know when to divide… or notdivide?– The cell has three inspection points, called___________________ checkpoints that provide feedbackwhich will _________ trigger or ____________ prevent theoccurrence of the next phaseChapter menuResourcesCopyright © by Holt, Rinehart and Winston. All rights reserved.

G 1 CheckpointGrowth• ____________________checkpoint• As long as the cell is_________ large enough and________________, healthy cellproteins called ________ cyclinswill trigger the synthesisof DNAChapter menuResourcesCopyright © by Holt, Rinehart and Winston. All rights reserved.

G 2 Checkpoint• DNA _______________checkpoint• DNA polymerasescheck and____________ correct anyerrors made whilecopying the DNA• If the DNA has beencopied correctly, cyclinswill trigger the start of_______________mitosissynthesisChapter menuResourcesCopyright © by Holt, Rinehart and Winston. All rights reserved.

• If too much damage has accumulated in the copiedDNA, another protein called _______ p 53 can haltdivision and signal for _____________________,apoptosiswhich is cell death…• Half of all human cancers result from a______________ or _______________ p53 proteinmalfunctioningabsentChapter menuResourcesCopyright © by Holt, Rinehart and Winston. All rights reserved.

M CheckpointMitosis• _____________checkpointexit• Triggers the _________from mitosis• Once cell division iscomplete, a cell willreenter the_____________ growth stageChapter menuResourcesCopyright © by Holt, Rinehart and Winston. All rights reserved.

Chapter 6Section 2 The Cell CycleWhen Control Is Lost: Cancer• Certain genes, called _________________,contain the information necessary to make theproteins that regulate cell growth and division.• If one of these genes is ________________ or________________, mutated cell reproduction may occurat an uncontrolled rate• The uncontrolled replication of cells results in_________________________canceroncogenesdamagedChapter menuResourcesCopyright © by Holt, Rinehart and Winston. All rights reserved.

• What are some factors that can damage or mutateyour cells?UV radiationsmokingpoor dietpesticidespollution– ___________________– ___________________– ___________________– ___________________– ___________________• Any factor that can cause your cells to mutate iscalled a __________________mutagenChapter menuResourcesCopyright © by Holt, Rinehart and Winston. All rights reserved.

• Once damaged…– The cell loses ______________ of the cell cyclerapidtumorcontrol– _________________ division occursnutrients– A ___________ forms, blocking ______________from reaching nearby healthy cells• If you develop cancer in somatic cells, like your lungcells, will your offspring inherit lung cancer?No…only mutations in the DNA ofsex cells are inheritedChapter menuResourcesCopyright © by Holt, Rinehart and Winston. All rights reserved.

Objective 1• Identify the major events that characterize eachof the five phases of the cell cycle– G 1– SGrowth and normal cell activitiesSynthesis of DNA– G 2– MitosisReplication of organellesSplitting of the nucleus– CytokinesisSplitting of the cytoplasmChapter menuResourcesCopyright © by Holt, Rinehart and Winston. All rights reserved.

Objective 2• Describe how the cell cycle is controlled in eukaryoticcellsThree checkpoints and proteins calledcyclins control the cell cycleChapter menuResourcesCopyright © by Holt, Rinehart and Winston. All rights reserved.

Objective 3• Relate the role of the cell cycle to the onset of cancerIf the cell loses control of the cell cycleand divides too quickly, cancer resultsChapter menuResourcesCopyright © by Holt, Rinehart and Winston. All rights reserved.