Cell Division and Mitosis

Lesson 8

Cell Cycle

Interphase MITOSIS Cytokinesis

I Pee Milk And Tea Constantly

Why cell division is IMPORTANT

• Without cell division, every living thing would be ONE CELL BIG

• ALL CELLS COME FROM OTHER CELLS

• Reasons for cell division1. So one celled organisms can make more

2. So multi-celled organisms can grow

3. So multi-celled organisms can replace old cells

4. So multi-celled organisms can heal wounds

The Cell Cycle

• Each cell goes through a series of steps from one division to the next

• The time between divisions or the length of each cycle can be different depending on the organism, the cell type, age

• Divided into interphase, MITOSIS, then cytokinesis

• MITOSIS – process where the nucleus divides to form two identical nuclei

Interphase• This is the part of the

cell life cycle when the cell is doing the job it was made to do.– Eukaryotic cells

spend most of their life in this phase

• Cells that cannot divide anymore (muscle and nerve cells) spend their entire lives in interphase

What’s happenin’? • The DNA is in its

chromatin form throughout interphase

• At the end…the cell makes exact copies of the DNA and organelles to prepare for cell division

PROPHASE

What’s happenin’?

1. the nucleolus and nuclear membrane disintegrate

2. DNA coils up into chromosomes

3. The two chromatids that makeup the chromosome are attached by a sticky protein called centromeres

4. The centrioles move to opposite ends of the cells

5. Spindle fibers stretch across the cell

METAPHASE

What’s happenin’?

1. The chromosomes line up across the center of the cell

2. They must line up across the midline of the cell so that each chromatid has a direct path toward the centrioles.

ANAPHASE

What’s happenin’?1. The centromeres of the

chromosomes divide

2. This causes the chromosomes to split into two chromatids

3. The separated chromatids move to the opposite ends of the cells

4. This separation is led by our tour guides, the centrioles

TELOPHASE

• What’s happenin’?

1. The spindle fibers disappear

2. The nuclear membranes reform around each new nucleus

3. The chromatids are huddling together in the newly forming nuclei

Cytokinesis

• NOT A PART OF MITOSIS

• Cyto – cell

• Kinesis – splitting

• This is just where the cytoplasm and cell membrane finish splitting in two.

The results of mitosis

• The cytoplasm and organelles will continue to separate until there are TWO new cells

• Each new human cell (except egg and sperm) has 46 chromosomes which is 23 pairs

• In animals, the cell membranes pinch apart at the end to make new cells

• In plant cells, there is a new cell wall/plate that forms between the new nuclei to make the new cells

• Practice math problem:

Start with one bacteria cell. This bacteria divides every 10 minutes. How many bacteria will you have after 1.5 hours?

Quiz

1. Put the following phases in order. Leave out any phases that do not belong.

Anaphase Prophase

Beriphase Telophase

Cellphase Cytokinesis

Metaphase Interphase

Karyphase Cytophase

2. Circle each phase of mitosis in YOUR list.

3. What does mitosis mean?