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  • Uploaded on Lesson 14b: Mitosis. Biology is the only subject in which multiplication is the same thing as division …. Making New Cells Making New DNA. Where it all began…. You start as a cell smaller than a period at the end of a sentence….

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Presentation Transcript
where it all began
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
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
Why do cells divide…
  • for reproduction
    • one celled organisms (clones)
  • for growth & development
    • fromfertilized eggto multi-celled organism
  • for repair
    • replace cells that

die or are lost


the cell cycle
The Cell Cycle

G1 = Resting and Growth

S = DNA is replicated

G2 = Growth & Prep

for Mitosis

M = Mitosis (cell division)

dividing cells
Dividing cells…
  • What has to be copied
    • DNA
    • organelles
    • cell membrane
    • lots of othermolecules
      • enzymes

plant cell

animal cell

remember this

Coil DNA into compact chromosomes

Copying DNA

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
copied paired up chromosomes
Copied & Paired Up Chromosomes

Single DNA strand

Single DNA strand being duplicated


Two new DNA strands linked by centromere

making one doubled chromosome.

cell prepares to divide

DNA in chromosomes




duplicated chromosomes


Cell Prepares to Divide

chromosomes are duplicated

Centromeres link chromosomes

4 single-stranded chromosomes

4 duplicated chromosomes

mitosis dividing dna cells
Mitosis: Dividing DNA & Cells
  • Stage 1: DNA Replication occurs.


DNA is copied!




mitosis dividing dna cells1
Mitosis: Dividing DNA & cells
  • Stage 2: DNA winds into chromosomes

Chromosomes are condensed!

duplicated chromosomes




mitosis dividing dna cells2
Mitosis: Dividing DNA & cells
  • Stage 3: Chromosomes line up in middle
    • attached to protein spindle fibers that will pull them apart.


are lined up!


mitosis dividing dna cells3
Mitosis: Dividing DNA & cells
  • Stage 4: Chromosomes separate
    • chromosomes split, separating the pairs
    • start moving to opposite ends (poles)

Chromosomesare separated!


mitosis dividing dna cells4
Mitosis: Dividing DNA & cells
  • Stage 5: Cytokinesis
    • cells start to divide
    • nucleus forms again

Cells Divide!


new daughter cell clones
New “daughter” cell CLONES
  • Get 2 exact copies of original cells
    • same DNA
    • “clones”

onion root tip


Any Questions??

Any Questions??

Virtual Lab 8 Mitosis in Plant Cells

Virtual Lab 9 Comparing Mitosis in Plant and Animal Cells

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