Cell UnitLT #3 I can DESCRIBE how

cells multiply.

Sam’s Puppy• Body cell reproduction involves producing

new daughter cells for growth of tissues as well as repair and replacement of old cells.

• Most living body cells eventually divide into two cells through a process called mitosis. This can happen because food and nutrients are broken down and become building blocks for new living materials like the new cells produced during cell division.

Why do cells divide?• Weeds can grow pretty fast. In

fact, the stems and roots of a fast-growing plant seem to get longer over night. Where do the new stem and root parts come from?–They are made when existing cells

divide to form new cells. This process is called cell division.

Why do cells divide?• Eventually cells need to

duplicate. There are two types of cell division, mitosis (growth) and meiosis (reproduction).

• Mitosis allows organisms to grow larger, and also helps organisms replace injured cells. GROWTH!

Mitosis• The big idea to remember is that

mitosis is the simple duplication of a cell and all of its parts.

• It duplicates its DNA and the two new cells (daughter cells: cells resulting from the replication and division of a single parent cell) have the same pieces and genetic code.

Two identical copies come from one original. Start with one; get two that are the same. Get the idea?

Mitosis• Before a eukaryotic cell (a cell

with an organized nucleus) divides, the genetic material in the nucleus of the cell copies itself.

• When the cell divides, the nuclear material splits in half so that each daughter cell gets genetic material that is the same as that of the parent cell.

Mitosis

• The dividing of the nuclear material is known as mitosis. • In the last stage of cell division, the cytoplasm divides as well.• There are now two complete

cells where there used to be one.

Science Alert!• The terms mitosis and cell

division are sometimes used interchangeably.

• BUT…mitosis really refers only to the dividing of the nuclear material.

• While…cell division is the complete process of copying and dividing the whole cell.

Cell Division Phases

• Beyond the idea that two identical cells are created, there are predictable stages or phases in the cell division process.

• These steps ensure that the new daughter cells are the same as the cell from which they formed.

Cell Division• There are 5 basic phases in the life-

cycle of a cell.

– Interphase–Prophase–Metaphase –Anaphase–Telophase

Cell Division Video of a Animal Cell

Cell Division• The following mnemonic devices can

help you remember the phases of cell division.• I prefer milk and tea.• I propose meeting at ten.• In Poland men are tall.

• CAN YOU COME UP WITH YOUR OWN mnemonic device?

Cell Division/Mitosis• Interphase –The stage before cell division starts.–As a cell prepares to divide, each

chromosome in the nucleus makes an exact copy of itself.

–Chromosomes: a structure made of DNA that contains the genetic info used to direct cell activity and make new cells

Cell Division/Mitosis• Prophase–The nucleus prepares for cell

division. –The genetic material shortens

and thickens.–The chromosome copies are held

together at their centers, so they form a sort of “X.”

Cell Division/Mitosis• Metaphase–The two copies of each

chromosome line up in the center of the cell.

Cell Division/Mitosis• Anaphase–The copies separate.–One complete set of chromosomes is

pulled to one side of the cell. –The other complete set is pulled to

the other side of the cell.

Cell Division• Telophase–Final stage of cell division–The cytoplasm pinches in at the

center of the cell, dividing the cell in half. –When cell division is complete, two

new daughter cells are formed.–The daughter cells are identical to

the parent cell.

Cell Division-Mitosis Stages-Video

Two identical copies come from one original. Start with one; get two that are the same. Get the

idea?

Bellringer

Please take a graphing worksheet and your

cursive practice from the wooden table and

complete silently at your desk.