Upload
sandra-rymer
View
213
Download
0
Embed Size (px)
Citation preview
Why do you think cells in all plants and organisms need to divide? To replace damaged tissue To increase in size (the organism) To reproduce
Repair
• Cells are constantly repairing themselves• If a cell can’t be repaired new ones are
produced to fill the void
Growth
• Cells are also what create our size• As we grow our cells are constantly
reproducing • If the reproduction rate is faster than normal,
we grow
ReproductionAsexual
• Done by somatic or body cells
• Done also by unicellular organisms
• Creates identical daughter cells
Sexual
• Done by gametes or sex cells
• Creates genetically different daughter cells
What does the DNA look like inside the nucleus of the cell?
• When the cell is not dividing, the DNA looks like a tangled mass called CHROMATIN
When the cell is ready to divide, the DNA condenses into CHROMOSOMES
• Chromosome: a compacted piece of chromatin that is used for cell division
• Sister Chromatids: A pair of identical Chromosomes
• Centromere: The center section where the sister chromatids are connected
Sister chromatids
Centromere
TE
M 3
6,60
0
LE 8-4
Sister chromatids
Centromere
TE
M 3
6,60
0
Sister chromatids
Chromosomedistribution
todaughter
cells
Chromosomeduplication
How do cells divide?
• Cell Cycle: an orderly sequence of events where cells divide
• The cell cycle consists of two major phases– Interphase (90% of the time)– Mitotic Phase/cell division (10% of the time)
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_the_cell_cycle_works.html
The Cell Cycle
In humans and other mammals, cells that reproduce daily have a cell cycle that usually lasts 10 to 20 hours.
Interphase
• Phase where all metabolic processes and functions happen– Ex:
• Cellular respiration• Protein creation• Movement• Growth• Other desired function
Interphase
• Interphase is also when the cell prepares for cell division– Ex:
• Increases proteins• Duplicates organelles• Grows in size• Replication (duplication) of DNA
Mitotic Phase
• The division phase of the cell• There are two main parts of M phase
– Mitosis – Cytokinesis
Mitotic phase
• Mitosis– The division of a cells nucleus and DNA into two
equal parts– Creates two daughter nuclei
• Cytokinesis– The division of the cells cytoplasm
• Together they create two identical daughter cells
Mitosis
• Prophase:– Sister chromatids are formed– Formation of spindle– Nuclear envelope breaks down
• Metaphase:– Sister chromatids line up– Spindle is formed and attaching to chromosomes
LE 8-6a
INTERPHASE PROPHASE PROMETAPHASE
Kinetochore
Fragmentsof nuclearenvelope
CentrosomeEarly mitoticspindleChromatin
Centrosomes(with centriole pairs)
LM
250
Nucleolus Nuclearenvelope
Plasmamembrane
Chromosome, consistingof two sister chromatids
Centromere Spindle microtubules
Mitosis
• Anaphase:– Separation of sister chromatids– Spindle pulls chromosomes to either side of the cell
• Telophase:– Spindle breaks down– Nuclear envelopes form (2)– Chromosomes loosen to become chromatin
• Cytokinesis:– After mitosis, cell pulls apart to create two
identical cells
LE 8-6b
METAPHASE ANAPHASE TELOPHASE AND CYTOKINESIS
Metaphaseplate
Spindle Daughterchromosomes
Nuclearenvelopeforming
Cleavagefurrow
Nucleolusforming
Cytokinesis in animal cells
Animal
• Formation begins with indentation
• Cell is pulled/ pinched until it breaks apart
Plants
• Formation begins with a disc containing cell wall materials
• A cell plate forms between the two nuclei
Cleavage furrow
Cleavagefurrow
Daughter cells
Cleavagefurrow
Contracting ring ofmicrofilaments
SE
M 1
40
Cytokinesis in plant cells• Formation begins with a disc containing cell wall materials• A cell plate forms between the two nuclei
Cell wall New cell wall
Daughter cellsCell plateVesicles containingcell wall material
Benign vs. malignant tumor• Benign tumor:
– abnormal mass of normal cells Malignant tumor:
• Masses of cells that result from the reproduction of cancer cells
• Cancer – Disease caused by cells that loose their ability to
control rate of division