Dec 25, 2015
Cell Division
All cells are derived from
New cells are produced for
This process will differ between prokaryotes and eukaryotes
Pre-existing cells
growth and to replace damaged or old cells
The instructions for making cell parts are encoded in the DNA, so each new cell must get a complete set of the DNA molecules
Each new cells will then have an identical copy of the DNA
• DNA must be copied or replicated before cell division
Tissue-
Organ- group of tissues that perform a
Organ system- multiple organs that work together
groups of cells that work together to perform a specific function
complex function
•Chromosomes are found in every cell of our body.
CHROMOSOMES
•In order to be alive, we need a full set of chromosomes = 46. (23 pairs of chromosomes)
•Each chromosome pairs up with its partner that looks identical to it (they both hold the same genes)
Chromosomes: rod-like structures in nucleus that contain hereditary information (DNA) & appear as long, thin threads called chromatin
Replication of an organism Cytoplasm divides equally into two Produces a new organism
Bacteria Amoeba Paramecium
Mitotic division of the cytoplasmOrganism develops a “bud” Cytoplasm does NOT divide
equally
Yeast Hydra
Organism can replace damage cells
OR Part of an organism grows into a
new organism
Lizard Starfish Planaria Lobster claws
A karyotype is a way for scientists to check chromosomes
Karyotypes are images of chromosomes to display their banding patterns.
Asexual 1 parent Offspring are
identical to parent & to each other
No special organs/cells
Process that divides cells = mitosis In one-celled
organisms = new organism
In multi-cellular organisms = growth & repair
Sexual 2 parents Fusion of sperm
& egg nuclei Offspring have a
combination of traits from both parents
Process that creates new cells = meiosis Produces
sperm & eggs
Is the division of the nucleus Only occurs in eukaryotes Doesn’t occur in some cells such as brain
cells
Occurs only in the body cells, known also as somatic cells
Results in 2 daughter cells which are identical to the parent cell AND each other
Why is Mitosis important for unicellular organisms? Form of reproduction
Every time an amoeba divides by mitosis a new identical amoeba is formed!
Cell specialization! Separate roles for each type of cell in the
body of a multi-cellular organism
Skin cells, muscle cells, liver cells
The Cell Cycle: a series of events that cells go through as they divide
Mitosis clip..\biomovies\mitosis part 1.mov
Part 2
A period of growth Occurs right before mitosis
Cell increases in size DNA is copied Organelles needed for cell
division are produced Then, mitosis (cell division)
occurs with 4 remaining phases:
•Chromatin condenses to form Chromosomes
•Chromosomes make a copy of themselves
•Spindle fibers grow • Nuclear membrane disappears
• Centrioles move to opposite ends of the cell
“AWAY” Doubled Chromosomes are
attached to spindle fibers• Chromatids get
ripped apart from each other
• Chromatids are pulled to opposite sides of the cell
The cell membrane pinches in
Each new cell is now in interphase
New nuclear membrane forms
Chromosomes unwind, pull up & become chromatin once again
Chromosomes on opposite sides of the
cell form 2 new nuclei.
Telophase
New Nuclear membranes!!
Mitosis 2
Cytokinesis (the Last step!)
• Last Step!! We’ve got to divide the rest of the cell!
• A new cell membrane forms between the cells & 2 Daughter Cells!!!!!
clip
2 identical cells/ no variety Mitosis Maintains Chromosome #
http://www.cellsalive.com/mitosis.htm
PROPHASE ANAPHASE
INTERPHASE
Animal Cell
Animal Cell The cell membrane is drawn inward They have centrioles Cytoplasm is pinched into 2 equal parts
Plant Cell Cell plate develops into a separating
membrane