Biology

Unit 8 – Cell Division

Notes #1 (Chapter 5)

Cell Division• For cells, bigger is not better

• As cells get bigger, volume increases faster than surface area

– This makes it difficult for the cell to take in enough nutrients and get rid wastes efficiently

• When a cell reaches its max size, the nucleus initiates cell division

Results of Cell Division

The cell cycle is important for:

•reproduction in some organisms

– asexual reproduction = identical offspring

• Regeneration (ex – sea star)

• Budding

• Fission

•growth in multicellular organisms

– Cell differentiation

•Repair replacement of worn out or damaged cells, and repair of damaged tissues.

The Cell Cycle (cont.)

• Most cells in an organism go through a cycle of growth, development, and division called the cell cycle.

• There are two main phases in the cell cycle—interphase and the mitotic phase.

Interphase occurs in three stages: G1, S, and G2, and takes up 90% of the time of the cell cycle

•G1 (gap 1)

– Period of growth, DNA = chromatin

•S (synthesis)

– Chromosomes replicate

Part 1 -Interphase

Part 1-Interphase – The cell’s DNA is

copied during the S stage and is arranged as pairs of identical chromosomes called sister chromatids.

– Sister chromatids are held together by a structure called the centromere.

• G2 (gap 2) Cell creates organelles

The Mitotic PhaseDuring mitosis, the contents of the nucleus divide, forming two identical nuclei.

The Mitotic Phase (cont.)

The Mitotic Phase (cont.)

The Mitotic Phase (cont.)

The Mitotic Phase (cont.)

The Mitotic Phase (cont.)

In cytokinesis, the cytoplasm divides (cell membrane folds in) and forms two new daughter cells.

Mitosis

Name that Stage!

Hint:

Chromosomes are aligned in middle of cell

Name that Stage!

Hint:

Cell plate is splitting the cell

Name that Stage!

Hint:

Two normal looking nuclei of two cells

Name that Stage!

Hint:

Chromosomes are forming and the nucleus is gone

Name that Stage!

Hint:

Chromatids are being pulled apart

Review1) In order, name the 5 stages of the cell cycle.

2) During which interphase stage do organelles replicate?

3) What do you call the division of the cell’s cytoplasm ?

4) During which interphase stage is DNA created?

5) During which stage do spindle fibers form?

6) During which stage are chromosomes aligned in the middle?

7) During which stage are chromatids separated?

8) During which stage does the nucleus dissolve?

9) What is the result of mitosis?

10) http://www.biology.arizona.edu/cell_bio/activities/cell_cycle/36m.html

1) In order, name the 5 stages of the cell cycle.– Interphase, Prophase, Metaphase, Anaphase, Telophase

2) During which interphase stage do organelles replicate?– G1

3) What do you call the division of the cell’s cytoplasm?– Cytokineses

4) During which interphase stage is DNA created? – S

5) During which stage do spindle fibers form? – Prophase

6) During which stage are chromosomes aligned in the middle? – Metaphase

7) During which stage are chromatids separated?– Anaphase

8) During which stage does the nucleus dissolve?– Prophase

9) What is the result of mitosis? – 2 identical (daughter) diploid cells