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

Asexual Reproduction2 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 cytoplasmOrganism develops a “bud” Cytoplasm does NOT divide

equally

Yeast Hydra

Spores are produced by the organism

/host

Spores released and grow into neworganism

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..\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

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!!

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

Chromosome number stays the same from generation to generation

2 “daughter cells” produced, each one identical to “mother cells”