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Name ________________________
Lakeland High School
Date _________________________
Biology/Ms. Tsai
Mitosis
Background –
All cells have DNA –
 What is DNA?
Our “blueprints”
The instructions for who and what we are
DNA is packaged into chromosomes
Every species has a unique number of chromosomes
Humans
______46____
Cat
_____ 38_____
Pig
___
38_____
Goat
___
60_____
Dog
____
78_____
Important: Chromosomes is specific for each species, and must be maintained for
the species to continue
Life of a cell
All living things have a life cycle, even cells.
Each cell has a beginning, a period of growth, and then an ending.
The first phase of the life cycle of a cell is interphase
During interphase, 2 things happen:
1.
cell grows
2.
chromosomes double----they each make an exact copy of itself
After interphase comes mitosis
During mitosis, cells divide to produce 2 exact copies of itself, resulting in one
parent cell becoming two daughter cells Error!
Purposes of mitosis
In one-celled organisms:
It is the way they reproduce - one organism becomes two
Key to remember is that all offspring produces this way are all the same –no
variation
In many celled organisms:
1.
Repair and replacement
2.
Growth and development
Mitosis – step by step
Before mitosis (cell division) actually begins, there is interphase
Cell grows:
And chromosomes replicate:
(make a copy)
So at the end of interphase, the cell looks like this:
Now mitosis begins:
There are 4 stages of mitosis: Prophase, Metaphase, Anaphase and Telophase
So, remember PMAT to remember them in order:
Prophase:
Nuclear membrane breaks down
Centriole move apart from each other & a spindle starts to form between
them
Metaphase:
Centrioles are at opposite ends of the cell
Chromsomes are lined up in the middle of the cell
Anaphase
The spindle fibers pull the chromosomes apart; each set is pulled toward
the opposite end of the cell
Telophase
Cell begins to “pinch in”
The nuclear membranes reform around the chromosomes, 1 at each end of
the cell
Cytokinesis
The cell now splits completely into 2 cells
We now have two cells, each identical to the original parent cell and to each other!
Summary Questions
1. What can we say about the daughter cells in mitosis compared to the parent cell?
2. What is the purpose of mitosis in unicellular organisms?
3. Name two ways in which mitosis is used in multicellular organisms
1.
2.
4. What is the phase of the cell cycle called where the cell is growing and the
chromosomes replicate?
5. In which stage of mitosis do the chromatids line up at the middle?
6. What would most likely result if mitosis was not followed by division of the
cytoplasm at the end (cytokinesis)?