Boo-yah Biology!
The Cell CycleMolecular Biology
Sumner HS
Cell Reproduction/Division
The ability of organisms to reproduce their kind is the one characteristic that best distinguishes living things from nonliving.
The continuity of life is based on the reproduction of cells, or cell division.
Cell Division Importance
Multicellular organisms depend on cell division for
Development from a fertilized cell
Growth
Repair or replacement of “bad” cells
Big Growth
We start as one cell
We end up being made of trillions of cells
They don’t magically appear **Poof!**
The result of countless cycles of growth and division of cells.
Question to ponder...
What tasks does a cell need to do in order to divide?
Have a 2nd copy of DNA
Have enough cytoplasm and organelles for a second cell
The Cell Cycle
Cells go through predictable, controlled patterns of growth or development and division.
Called the cell cycle
The Cell Cycle
Cell 2
Big Picture
Interphase/
MitosisCell 1
Cell 1
Cell 2
Big Picture Cont’dInterph
ase/Mitosis
Cell 1
Cell 1
Cell 3
Interphase/
Mitosis
Cell 2
Cell 4
Cell Cycle Major Phases
Interphase = period of growth, DNA replication and protein synthesis
Mitosis = cell division
Interphase
Interphase can be divided into subphases
G1 phase
S phase
G2 phase
G1 Phase
Rapid growth
High metabolic activity
Making lots of proteins
S Phase
DNA is copied (replicated)
Cell has twice the number of normal chromosomes.
Cell keeps growing
G2 Phase
More proteins made
Mitochondria & other organelles replicate
Cell keeps growing
Summarize
In your own words, summarize each of the phases of interphase.
Mitotic Phase
The Mitotic Phase has two major phases
Mitosis has four sub-phases
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
New Note Instructions
For each of the phases of cell division...
....don’t write down the details I put up
Instead, prepare to summarize the main events in about 10 words.
Prophase
Chromosomes coil up and become visible (twisted rubber band)
Centriole begins to form spindle, made from same material as cytoskeleton.
Nuclear envelope and nucleolus begin to disappear
Summarize!
Metaphase
Chromosomes move to “equator” of the cell
Each half of the chromosome is attached to a spindle fiber at the centromere.
Centromere is a protein that joins the two “sister” chromatids, or replicated chromosome pairs
Summarize!
Anaphase
Sister chromatids are pulled apart to opposite ends of the cell.
Each chromatid is now a separate chromosome.
Summarize!
Telophase
Genetically identical daughter nuclei form at opposite ends of the cell
Nuclear envelope begins to reappear.
Summarize!
Cytokinesis
In animal cells, cytokinesis occurs by a process known as cleavage, forming a cleavage furrow.
A “string” of cytoskeleton pinches the cell in two
Summarize!
Cytokinesis cont.
In plant cells, a cell plate forms between the cells after telophase.
Mitosis results in Mitosis results in
two identical cellstwo identical cells
called called daughter daughter cellscells
Mitosis results in Mitosis results in
two identical cellstwo identical cells
called called daughter daughter cellscells
Real Pictures: Early Prophase
Real Pictures: Late Prophase
Real Pictures: Metaphase
Real Pictures: Anaphase
Real Pictures: Early Telophase
Real Pictures: Late Telophase
Test Yourself
Identify prophase, metaphase, anaphase Identify prophase, metaphase, anaphase and telophase in these cells.and telophase in these cells.
Check Your KnowledgeCheck Your Knowledge