The Cell Cycle and MitosisThe Cell Cycle and Mitosis
What is Mitosis?What is Mitosis?
Mitosis is the process by which eukaryotic cells divide.
Prokaryotes divide through a simpler process called binary fission.
What is the purpose of What is the purpose of Mitosis?Mitosis?
When single celled organisms go through mitosis, they are reproducing: there are now two new organisms (asexual reproduction).
Multicellular organisms go through mitosis to produce new cells to grow or to replace dying or damaged cells (growth and repair).
Human DevelopmentHuman Development
Sperm Motility
Cleavage and Implantation
Development of a fetus
Key termsKey termsChromosome- structure made of
highly coiled or condensed DNA.Chromatin – the uncoiled form of
DNA.Sister chromatids – two identical
sections (copies) of DNA joined together at the centromere.
Pictures on next slide
Often confused termsOften confused terms 1. Single strand of
chromatin (DNA’s normal structure in the nucleus)
2. Two sister chromatids joined at centromere (After replication)
3. Replicated or double stranded chromosome after condensation. Each half is still considered a sister chromatid (During the cell cycle)
Gap1 Synthesis Prophase
1 2 3
What is the cell cycle?What is the cell cycle?All cells pass through a series of
events called the cell cycle.Some cells cycle continually, other
cell types only a limited number of times before they die.
Cell CycleCell CycleOnly one hour out of 22 is spent in active division (Mitosis)Depending upon the type of cell undergoing the cycle.
Relationship of StagesRelationship of StagesInterphase
consists of:Gap 1 (G1)Synthesis (S)Gap 2 (G2)Total time : 21
Hours
Mitosis consists of:ProphaseMetaphaseAnaphaseTelophaseTotal time : 1 Hour
InterphaseInterphase Typical Cell spends
95% of its time in interphase
Centrioles replicate during Gap 1
DNA copies itself during Synthesis
Growth occurs during all three phases.
WhatWhat’’s the DNA s the DNA doing?doing?
Chromatin in Gap 1Replicates in
SynthesisCondenses into
chromosome during early mitosis (prophase).
ProphaseProphaseChromatin starts to coil into
chromosomesNucleus, Nucleolus and Nuclear
membrane (N guys) start to dissolve
Centrioles moving to opposite ends of cell
By end, chromosomes fully formed, N guys gone, and centrioles at opposite ends of cell.
MetaphaseMetaphaseAll chromosomes line up
on equator of cellSpindle fibers attach to
each chromosome
AnaphaseAnaphase Spindle fibers contract
and pull sister chromatids apart
Full set of DNA eventually pulled to opposite ends of cell.
TelophaseTelophaseChromosomes begin to uncoilNuclear membrane begins to reformIn plants, cell plate forms to divide
cytoplasmIn animals, cleavage furrow forms
to divide cytoplasm