If cancer is uncontrolled cell division…why would a cell divide in the first place? Brainstorm a list of reasons a cell would divide.

Why would a cell divide? DNA “overload” Trouble exchanging materials Repair an injury Replace old worn out cells Asexual reproduction Organism = growth

The Cell Cycle The series of events that cells go through as they grow and divide.

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Where does cell division occur? Most cells are able to divide… But some cannot, like: Most nerve cells Brain cells Heart cells Blood cells

Cut out your cells and place them in chronological order. Glue them in your notebook once you have approval.

What is the end product of mitosis?

Steps of the cell cycle

Step One: copy the DNA Stop and think: why would it be important to do this each time?

Step Two: Split the DNA equally between the 2 cells

Step three: Split the cell’s contents

Life Cycle of a Cell

Before a growing cell becomes too large it divides The division results in two essentially identical cells called “daughter cells”.

Prior to division the cell replicates all of its DNA. Replication solves the problem of information storage, each daughter cell receives its own genetic information

Why would it be important that the cell copies itself before dividing??? What would happen if a cell split into two without copying itself? Would both sides survive?

Phases of Mitosis

Interphase In interphase the DNA in the nucleus is in a loose stringy form called chromatin DNA replication takes place, copying itself to get ready for mitosis

Prophase During prophase chromosomes become visible, centrioles take position on opposite sides of the nucleus Nucleus disappears and the nuclear envelope breaks down

Metaphase Chromosomes begin to line up across the center of the cell Each chromosome is now connected to a spindle fiber at its centromere

Anaphase The centromeres that join the sister chromotids separate creating two individual chromosomes Chromosomes continue to move until the have separated into two groups near the poles of the spindle

Telophase The chromosomes gather at opposite ends of the cell Chromosomes begin to lose their distinct shape Two new nuclear membranes form

Cytokinesis Cytokinesis is the division of the cytoplasm Occurs at same time as telophase (not a different step in mitosis) Done a little different in plant and animal cells

P rophase M etaphase A naphase T elophase