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Cell Reproduction
Prokaryotes Bacteria
Eukaryotes Plants & animals
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2. Prokaryotes (Bacteria)
REMEMBER:
Lack a nucleus
Have a single round chromosome
Reproduce by binary fission
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Binary Fission
Only used by bacteria
Cells increase their cell mass slightly
DNA & cell components are replicated and sorted in equal parts
Each cell divides into 2 daughter cells
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4. Binary Fission of Bacterial Cell
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Growth animation

5. E. Coli Dividing by Binary Fission
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Eukaryotes
REMEMBER-
Contain a nucleus & membrane bound organelles
Continually go through the cell cycle
Asexually reproduce cells by mitosis
Sexually reproduce new organisms by meiosis
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Cell Cycle
Cell cycle is the stages of growth & division
NO beginning or end!
Interphase
G1 Phase
S Phase
G2 Phase
M(itosis) Phase
Cytokinesis
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8. Interphase – Resting Stage
Cells carrying on normal activities i.e metabolism
Individual chromosomes aren’t visible
Three subphases (G1, S, G2)
Two checkpoints to control growth

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Interphase
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G1 Phase
First growth stage
Cell increases in size
Cell prepares to copy its DNA
G1/S Checkpoint at the end
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11. G1/S checkpoint G1/S checkpoint is most critical
primary decision point
“restriction point”
if cell receives “GO” signal, it divides
internal signals: cell growth (size), cell nutrition
external signals: “growth factors”
if cell does not receive signal,
it exits cycle & switches to G0 phase
non-dividing, working state

12. G0 phase G0 phase non-dividing, differentiated state
most human cells in G0 phase
liver cells
in G0, but can be “called back” to cell cycle by external cues
nerve & muscle cells
highly specialized
arrested in G0 & can never divide

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S(ynthesis) Phase
Copying of all of DNA’s instructions
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14. Duplicated Chromosome
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G2 Phase
Second growth stage
Replicates organelles
Proteins needed for cell division (M phase) produced
G2/M Checkpoint to ensure DNA has been properly synthesized and cell is ready
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M Phase
Cell growth & protein production stop
Cell’s energy used to make 2 IDENTICAL daughter cells
Called mitosis or karyokinesis (nuclear division)
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Stages of Mitosis
Preparation for division
Separation of Chromosomes
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18. Cells Undergoing Mitosis
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19. Prep for Division Must remove barriers like nucleus
Neatly coil up chromosomes so they can easily be separated
Attach machinery/proteins necessary to divide chromosomes evenly (spindle fibers)
Spindle checkpoint to make sure everything is connected properly

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Mitotic Spindle
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Human Chromosomes
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22. Separation of chromosomes
SISTER CHROMATIDS are pulled apart at centromere by the spindle fibers
Shortest stage
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Cytokinesis
Division of cytoplasm
Reform nucleus, recycle proteins used, etc
Forms a cell plate (plants) or cleavage furrow (animals)
Eventually forms two, identical daughter cells
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       Plant            
Animal
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25. Frequency of cell division
Frequency of cell division varies by cell type
embryo
cell cycle < 20 minute
skin cells
divide frequently throughout life
12-24 hours cycle
liver cells
retain ability to divide, but keep it in reserve
divide once every year or two
mature nerve cells & muscle cells
do not divide at all after maturity
permanently in G0

26. Cancer
When a cell fails checkpoints BUT continues to divide – generally, cancer!!
Proto-oncogenes – genes that that control the cell cycle
Oncogenes – genes that mutated and no longer control the cell cycle
Mutations are caused by lots of things – chemicals, UV radiation, genetics, heat, etc