Download Cell Division

Wednesday 11/4/15
Learning Goal:
Identify the events take place during the three stages
of the cell cycle.
Warm-up:
When an organism grows, what is happening to their
cells?
Homework:
Finish pages 28-30 if you didn’t finish in class
Cell Division
CHAPTER 3 SECTION 5
Cell Cycle
 The regular sequence of growth and division that
cells undergo



Cell grows
Prepares for division
Divides into two new cells, “daughter cells”
 Three main stages:
 Interphase
 Mitosis
 cytokinesis
Stage 1: Interphase
 Period before cell division
 The cell grows to full size
 Replicates
Makes an EXACT copy of its DNA in its nucleus
 Each daughter cell must have a complete set of DNA to survive
 End of replication, cell contains two identical sets of DNA


Prepares to divide
Stage 2: Mitosis
 Mitosis
 The second stage of the cell cycle
 Cell’s nucleus divides into two new nuclei
 One copy of the DNA is distributed into each of the two
daughter cells
 4 Parts of Mitosis
 Prophase
 Metaphase
 Anaphase
 Telophase
4 Parts of Mitosis
 Prophase
 Threadlike chromatin in the nucleus condenses to form
double-rod structure called chromosomes
Each chromosome has two rods, due to replication
 Each identical rod in a chromosome is called a chromatid
 Two chromatids are held together by a centromere

4 Parts of Mitosis
 Metaphase
 The chromosomes line up at the center of the cell
 Each chromosome attaches to a spindle fiber at its centromere
4 Parts of Mitosis
 Anaphase
 The centromeres split
 The chromatids separate by spindle fibers (go to opposite ends
of the cell)
4 Parts of Mitosis
 Telophase
 Chromosomes begin to stretch out, lose rodlike appearance
 Nuclear envelope forms around each region of chromosomes
Stage 3: Cytokinesis
 Cytokinesis



Final stage of the cell cycle
The cytoplasm divides
Organelles are distributed into each of the two new cells
The cell will then enter interphase… and the cycle begins
again.
 Cytokinesis in Animal Cells: cell membrane
squeezes together
 Cytokinesis in Plant Cells: cell wall cannot squeeze
together, a cell plate forms that gradually will develop
into the cell membrane
The Structure of DNA
 Looks like a twisted ladder,
or spiral staircase
 The sides of the ladder are
made up of


Deoxyribose (sugar)
Phosphate
 Each rung of the ladder is
made up of a pair of
molecules called nitrogen
bases


Adenine (A) Thymine (T)
Guanine (G)  Cytosine (C)
The Replication Process
 The two sides of the DNA molecule unzip and
separate
 Nitrogen bases floating in nucleus pair up with the
bases on each half of the DNA molecule
 New bases attach, two new DNA molecules form