http://www.simpletruths.tv/store/movies.php?movie=fstr

Biology is the only subject in which

multiplication is the same thing as division…

2006-2007

Lesson 14b: Mitosis

Making New CellsMaking New DNA

2006-2007

Where it all began…You start as a cell smaller than a period at the end of a sentence…

And end up as a full grown adult with billions of cells!

Getting from there to here…• Going from egg to baby….

the original fertilized egg has to divide… and divide…

and divide…and divide…

Why do cells divide…• for reproduction

– one celled organisms (clones)• for growth & development

– from fertilized egg to multi-celled organism• for repair

– replace cells that die or are lost

amoeba

The Cell CycleG1 = Resting and Growth

S = DNA is replicated

G2 = Growth & Prep for Mitosis

M = Mitosis (cell division)

Dividing cells…• What has to be copied

– DNA– organelles– cell membrane– lots of other

molecules• enzymes

animal cellplant cell

Remember this?• When a cell is ready to divide it must…

– copy DNA first (DNA Replication), then…– coil up doubled chromosomes

like thread on a spool…• now can move DNA around cell without having it tangle

& break

Copying DNA

Coil DNA into compact chromosomes

Copied & Paired Up Chromosomes

centromere

Single DNA strand

Single DNA strand being duplicated

Two new DNA strands linked by centromere making one doubled chromosome.

Cell Prepares to Divide

nucleus

cell

DNA in chromosomes

nucleus

cellduplicated chromosomes

chromosomes are duplicated

4 single-stranded chromosomes

4 duplicated chromosomes

Centromeres link chromosomes

Mitosis: Dividing DNA & Cells• Stage 1: DNA Replication occurs.

nucleus

cell

DNA

DNA is copied!

INTERPHASEINTERPHASE

Mitosis: Dividing DNA & cells• Stage 2: DNA winds into chromosomes

nucleus

cell

duplicated chromosomes

Chromosomes are

condensed!

PROPHASEPROPHASE

Mitosis: Dividing DNA & cells• Stage 3: Chromosomes line up in middle

– attached to protein spindle fibers that will pull them apart. Chromosomes

are lined up!

METAPHASEMETAPHASE

Mitosis: Dividing DNA & cells• Stage 4: Chromosomes separate

– chromosomes split, separating the pairs– start moving to opposite ends (poles)

Chromosomes

are separated!

ANAPHASEANAPHASE

Mitosis: Dividing DNA & cells• Stage 5: Cytokinesis

– cells start to divide– nucleus forms again

Cells Divide!

TELOPHASETELOPHASE

New “daughter” cell CLONES• Get 2 exact copies of original cells

– same DNA– “clones”

Mitosis in whitefish embryo

Mitosis in plant cell

onion root tip

http://www.cellsalive.com/mitosis.htm

Overview of mitosis

Any Questions??

Any Questions??

Virtual Lab 8 Mitosis in Plant CellsVirtual Lab 9 Comparing Mitosis in Plant

and Animal Cells

Draw, label and explain mitosis as shown on pages 246-247 in your text.