Mitosis “The Life and Times of the Cell”
Feb 14, 2016
Mitosis
“The Life and Times of the Cell”
Objectives
List factors that influence when cells divideUnderstand & describe the ‘Cell Cycle’Study the events of cell division (Mitosis)Compare Mitosis in plant & animal cells
Cell Division Animation
Reading Assignment
Read Section 10-1, p.241-243 titled Cell Growth.From the diagram indicating the Ratio of Surface area to Volume onp.243, sketch in your notes the smallest cell and the related statistics for Surface Area, Volume, and Surface Area to Volume Ratio and then sketch the largest cell with it’s related statistics.Answer the 4 questions in 10-1 Section Assessment on p.243.
Cell Cycle – 4 PhasesGap 1 (G1)– Typical cell growth &
metabolism.S Phase (S)– DNA Replication
Gap 2 (G2)– Centrioles Replicate– Protein synthesis
M Phase (M)– Mitosis phase / cell division
occurs
Cell Cycle
The G1, S and G2 stages of the Cell Cycle happen during INTERPHASE.The M phase consists of: Prophase;
Metaphase; Anaphase;
Telophase; Cytokinesis
S Phase - DNA ReplicationAn enzyme called Helicase causes the hydrogen bonds that hold DNA together to break or ‘unzip’
Then DNA Polymerase allows free floating nucleotides to attach to the single strand of DNADNA is Replicated
Draw DNA Replication
Draw a DNA triplet with the base sequence ATG on the left side. Make the 5’ the top left.
DNA Replication
Separate the original DNA strands.With different colors, show the attachment of free-floating nucleotides.
DNA Replication
Where do the free-floating nucleotides come from?Foods we eat!How do the 2 strands compare?They are exactly the same!What happens if there is a mistake made during replication?A mutation occurs!
Replication
DNA Replication..Who wants to try?
Replication Song
M Phase – Mitosis (4/5 Phases)
1. Interphase– G1, S, & G2 phases
2. Prophase– Early & Late
3. Metaphase4. Anaphase5. Telophase– Early & Late
Cytokenesis
Interphase
Early ProphaseReplicated centrioles split and start moving to opposite sides of the cell forming ASTERS.Nuclear envelop disappearsReplicated chromatin shortens, thickens and forms CHROMATID PAIRS
Remember this Diagram?
Early Prophase
Late Prophase
Centrioles have reached opposite poles of the cell
SPINDLE forms
Chromatid Pairs float throughout the cytoplasm.
Late Prophase
MetaphaseShortest stage of Mitosis
Chromatid pairs align at the equator of the spindle
Metaphase
Anaphase
Chromatid pairs split
Spindle fibers contract and the single CHROMOSOMES are pulled to opposite poles
Anaphase
Early TelophaseOften described as the opposite of prophase
Nuclear envelop reappears
The chromosomes unravel to become chromatin
Cleavage furrow begins to form
Late Telophase
Cleavage furrow completes it’s indentation.“Mother” cell splits into 2 identical “Daughter” cells in a process called CYTOKINESIS
Early/Late Telophase
Summary of MitosisProphase:
Replicated chromatin condense into chromatid pairCentrioles move to opposite polesNuclear envelope disappearsSpindle fibers start to form
MetaphaseChromatid pairs line up at the equator
AnaphaseChromatid pairs splitChromosomes are pulled to opposite poles by the spindle fibers
TelophaseChromosomes de-condense into chromatinNuclear envelope reappearsCytoplasm is divided into 2 cells Cytokinesis
Mitosis
I don't watch television when I can talk about Cell Division!
One more Phase – GAP 0 (G0)Some cells do not replicate their centrioles during Prophase.
They lose their ability to divide
They enter the Gap 0 stage
Neurons of the Spinal cord / Brain cells
Mitosis in Plant vs. Animal CellsThe Rivalry Continues
Plants have no centrioles but still form spindle fibersPlant cells divide from the inside outCell Plate“Messy Metaphase”
Plant Cell Mitosis
Importance of Mitosis
Method of reproduction for all single celled organisms
Allows us to regenerate cells (tissue) repair cuts, bone breaks, etc
Growth – one cell to trillions
How Long does the Cell Cycle Last?
Pick up a textbook and turn to page 249.
Read the section titled “Life Spans of Cells” and answer the 4 questions that follow.
Regulating the Cell Cycle
Turn in your textbook to page 250. Read pages 250 to 252.Answer the 5 questions that follow.
Terms: Contact Inhibition; Cyclins; Internal regulators; External regulators; Cancer;