The Cell Cycle

Steps in the cell cycle

Interphase: No division occurs. Interphase has three subdivisions: G1 S G2

Interphase

G1: Gap one first phase, Growth and normal processes take place. No division occurs Longest phase of interphase

Interphase

S or Synthesis phase: Second stage DNA replicates

making another copy of chromosomes.

At the end of this phase, the nucleus will contain two complete sets of DNA.

Interphase

G2: Cells prepare for division. Shortest stage of interphase Spindle fibers, centrioles, etc - are prepared

for next stage

Interphase

Mitosis

Mitosis: the division of the cell nucleus and its contents. Mitosis has four main stages: Prophase Metaphase Anaphase Telophase

Parent cell

Mitosis

Cytokinesis

Daughter cells

Mitosis

Prophase: Chromosomes become shorter, thicker, and become visible. Nuclear envelope begins to disappear. Centrioles are moving toward poles and

spindle fibers are forming. Spindle fibers form between centrioles.

Prophase

Mitosis

Metaphase: The chromosomes line up in the mid-plane of the cell. Spindle fibers attach to the centromere of

the chromosome.

Mitosis

Anaphase: Sister chromatids separate at centromeres and move away One group of chromosomes are pulled by

the centrioles on the spindle fibers

Anaphase

Mitosis

Telophase: Chromosomes are at the poles. The nuclear envelopes begin to form. Nucleolus reforms Spindle fibers disappear

Cytokinesis and telophase take place around the same time.

Telophase

Cytokinesis

Cytokinesis: The process that divides the cytoplasm. Animal cells - The cell membrane pinches

together

Plant Cells

In plant cells cytokinesis occurs by forming a cell plate to form the new cell wall.

QuickTime™ and a decompressor

are needed to see this picture.

Answer the following questions

1. Is this an animal or a plant?

2. What phase is this slide in?

3. What helped you determine which phase this slide was in?

Answer the following4. Is this an animal or

a plant?

5.What phase is this slide in?

6. What helped you determine which phase this slide was in?

Answer the following

7. Is this an animal or a plant?

8.What phase is this slide in?

9. What helped you determine which phase this slide was in?

Answer the following

10.Is this an animal or a plant?

11. What phase is this slide in?

12. What helped you determine which phase this slide was in?

Answer the following

13.What phase is the cell the arrow is on in?

14.What phase is the cell to the left of that cell in?

15. Name the two differences between plant mitosis and animal mitosis.

Review

Four main stages of the cell cycle: G1- normal growth Synthesis- DNA is copied Gap 2- more growth Mitosis- nuclear division

Prophase- chromosomes are visible, nuclear envelope disappears

Metaphase- chromosomes line in up in mid-plane Anaphase- chromosomes move away from the mid-plane Telophase- Chromosomes at poles nuclear envelope forms

Cytokinesis- divides the cytoplasm

Together, these three stages make up interphase.