Cell Division Pre-existing cells growth and to replace damaged or old cells

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

 Asexual Reproduction  2 daughter cells produced from a parent cell

 Replication of an organism  Cytoplasm divides equally into two  Produces a new organism  Bacteria  Amoeba  Paramecium

 Mitotic division of the cytoplasm  Organism develops a “bud”  Cytoplasm does NOT divide equally  Yeast  Hydra

 Spores are produced by the organism /host  Spores released and grow into new organism  Bread mold

 Organism can replace damage cells OR  Part of an organism grows into a new organism  Lizard  Starfish  Planaria  Lobster claws

Spiny Brittlestar Regenerating arm

 Occurs in plants  Part of a root, stem or leaves  Grows into a new plant  Bulbs

“All cells arise from preexisting cells” (Virchow)

A karyotype is a way for scientists to check chromosomes Karyotypes are images of chromosomes to display their banding patterns.

NORMAL KARYOTYPE

Sex Chromosome ABNORMAL KARYOTYPE Down Syndrome

Sister chromatids Centromere

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..\bi omovie s\mitosi s part 1.mov..\bi omovie s\mitosi s part 1.mov Part 22

 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

These are homologous pairs of chromosomes in the nucleus Cell Membrane Prophase

 Meta = middle  Chromatids line up in middle on “equator”  Spindle fibers attach to centromeres

centrioles Doubled chromosomes line up in the center of the cell. Cell Membrane Metaphase

 “AWAY”  Doubled Chromosomes are attached to spindle fibers Chromatids get ripped apart from each other Chromatids are pulled to opposite sides of the cell

Cell Membrane Anaphase

 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!! MitosisMitosis 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 # 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

 Chromosome number stays the same from generation to generation  2 “daughter cells” produced, each one identical to “mother cells”