Chapter 12: The Cell CycleWhy do cells need to divide?As they grow larger, their surface area-to-volume ratio decreases. It is therefore more difficult to transport all needed materials in/out of the cell! A large cell is an inefficient cell.

When is cell division important?Reproduction unicellular organisms binary fission in bacteriaGrowth & development from fertilized eggRepair (& replacement) of damaged cellsChapter 12: The Cell Cycle

When is cell division important?What is an organisms genome?Total hereditary endowment (all genes) in the cell of a speciesNuclear & extra-nuclear (mito & chloro)How many chromosomes do we have?46 somatic cell (cells of the body) 2n diploid23 gamete (sex cells sperm & egg) n haploidWhat are chromosomes made of?ChromatinDNA & proteinsChapter 12: The Cell Cycle

Fig 12.4 Chromosome duplication & distribution during cell division

When is cell division important?What is an organisms genome?How many chromosomes do we have?What are chromosomes made of?What are the 2 major phases of the cell cycle?Interphase 90%Mitotic phase 10%Chapter 12: The Cell Cycle

When is cell division important?What is an organisms genome?How many chromosomes do we have?What are chromosomes made of?What are the 2 major phases of the cell cycle?InterphaseMitotic phaseWhat are the steps of the cell cycle?IPMATCInterphaseProphaseMetaphaseAnaphaseTelophaseCytokinesis

Chapter 12: The Cell Cycle

Combine pro- & prometaphaseChromosomes appear as Pairs

MiddleApartTwo

Chapter 12: The Cell CycleKinetochores:Located near centromeres of sister chromatids; microtubules attach here Microtubules:Make up spindle fibers; framework on which chromosome movement occursMotor Proteins:Located within kinetochores; move chromosomes apart during AnaphaseActin Filaments:Interact with myosin to create cleavage furrow/pinching during cytokinesis in animal cells

When is cell division important?What is an organisms genome?How many chromosomes do we have?What are chromosomes made of?What are the 2 major phases of the cell cycle?What are the steps of the cell cycle?What is the difference between animal and plant cytokinesis?Animal cleavage furrow cell forms from outside inPlants cell plate cell forms from inside out

Chapter 12: The Cell Cycle

Figure 12.9 Cytokinesis in animal and plant cells

When is cell division important?What is an organisms genome?How many chromosomes do we have?What are chromosomes made of?What are the 2 major phases of the cell cycle?What are the steps of the cell cycle?What is the difference between animal and plant cytokinesis?How is the cell cycle regulated?CheckpointsMake sure cell has enough ingredients to move to next stage

Chapter 12: The Cell Cycle

Figure 12.14 Mechanical analogy for the cell cycle control system

Figure 12.15 The G1 checkpointMost functioning cells are in G0

When is cell division important?What is an organisms genome?How many chromosomes do we have?What are chromosomes made of?What are the 2 major phases of the cell cycle?What are the steps of the cell cycle?What is the difference between animal and plant cytokinesis?How is the cell cycle regulated?CheckpointsMake sure cell has enough ingredients to move to next stage Cyclins Cyclin-dependent kinase (CDK)MPF maturation promoting factor Cyclin + CDK = MPF

Chapter 12: The Cell Cycle

Accumulated cyclin moleculescombine with recycled Cdk mol-ecules, producing enough molecules of MPF to pass the G2 checkpoint and initiate the events of mitosis.Fig. 12.16 Molecular control of the cell cycle at the G2 checkpoint