cell division chapter 10. why do you think cells in all plants and organisms need to divide? to...
Post on 15-Dec-2015
213 Views
Preview:
TRANSCRIPT
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
top related