Cell Division
The Cell Cycle- The regular sequence
of growth and division that cells
undergo.
Three stages of the Cell Cycle
1. Interphase
2. Mitosis
3. Cytokinesis
Interphase-Period before Division
Occurs.
• Growth
• DNA Replication
• Preparation for Division
Growth
• Cell Doubles in size and produces structures
necessary to carry out functions.
• Organelles become more numerous.
DNA Replication
• The cell makes a copy of the DNA in its
nucleus.
Preparation for Division
• The cell produces a spindle network of fibers
and centrioles that it uses to facilitate divison.
Mitosis-Stage where the cell’s nucleus
divides into two new nuclei.
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Prophase
Metaphase
Anaphase
Telophase
Prophase
• The chromatin condenses to form
Chromosomes. The nuclear membrane breaks
down.
Metaphase
• The chromosomes line up across the center of
the cell. Each chromosome attaches itself to a
spindle fiber.
Anaphase
• The centromeres split and the two chromatids
separate. The matching chromatids move to
opposite ends of the cell.
Telophase
• The chromosomes begin to stretch out and
lose rodlike appearance. A new nuclear
membrane forms around each region of
chromosomes.
Cytokinesis
• The cytoplasm divides, distributing the
organelles into each of the two new cells.
• In animal cells the membrane pinches in at
the middle of the cell until they become two.
• In plant cells, a cell plate forms dividing the
two. Then the membranes form and the cell
walls form.
DNA Replication
• DNA carries all of the cell’s instructions.
• Each cell gets its own set.
The Structure of DNA
• DNA molecule looks like a twisted latter
• Called a double helix.
DNA composition
• Sugars called Deoxyribose alternate with phosphates
on the sides of the DNA ladder.
• Nitrogen base pairs make up the rungs of the ladder.
Adenine pairs with Thymine. Cytosine pairs with
Guanine.
The Replication Process.
• DNA unwinds and unzips. New nitrogen bases move in
to pair with the bases that remained attached to the
rungs. Because the bases pair with their match the
one DNA becomes two.