AH Biology - Unit 1 - KA5(b) - The Cell Cycle

What does the cell cycle consist of?

The cell cycle consists of:

• Interphase

• Mitotic (m) phase

What are the three main phases of interphase?

The three main phases of interphase are:

• G1 - The first growth phase

• S - The phase where DNA is replicated (synthesised)

• G2 - The second growth phase

What are the two phases of the mitotic phase?

The two phases of the mitotic phase are:

• Mitosis - Prophase, Metaphase, Anaphase, and Telophase

• Cytokinesis (cell division)

During mitosis, what happens to chromosomal material?

During mitosis, chromosomal material is separated by spindle microtubules (spindle fibres)

What is mitosis?

Mitosis is the separation of chromosomal material by spindle microtubules followed by cytokinesis. Cytokinesis is the separation of the cytoplasm to form two identical daughter cells.

What are the phases of the cell cycle?

The phases of the cell cycle are:

• Interphase

• Prophase

• Metaphase

• Anaphase

• Telophase

• Cytokinesis

Describe interphase

Interphase is the phase where the cell spends most of it’s time. It has three phases:

• G1 - The first growth phase

• S - The phase where DNA is replicated (synthesised)

• G2 - The second growth phase

Describe prophase

In prophase:

• DNA condenses into chromosomes of two sister chromatids.

• The nuclear membrane breaks down.

• Spindle microtubules radiate from the MTOC by polymerisation and attach to chromosomes via their kinetochores in the centromere.

Describe metaphase

In metaphase:

• Chromosomes align at the metaphase plate, the spindles equator.

Describe anaphase:

In anaphase:

• Sister chromatids are separated as spindle micro-tubules shorten by depolymerisation and chromosomes are pulled to opposite poles.

Describe telophase

In telophase:

• The chromosomes decondense and nuclear membranes are formed around them.

Describe cytokinesis

In cytokinesis:

• The cytoplasm is split in two to form two identical daughter cells.